SOUTHWEST GAS CORP

Note 1 - Background and Organization

Nature of Operations. This is a combined annual reportof the Company and Southwest Gas. The combined notes to the consolidated financial statements apply to the Company and Southwest Gas unless otherwise described. Southwest Gas Holdings, a Delaware corporation, is a holding company owning all of the shares of common stock of Southwest Gas; until April 22, 2024, all of the shares of common stock of Centuri Holdings, Inc. (“Centuri”); and until February 14, 2023, all of the shares of common stock of MountainWest.

The Company’s businesses were managed within three separate reportable segments until February 2023, our Natural Gas Distribution segment (Southwest Gas), our Utility Infrastructure Services segment (Centuri), and our Pipeline and Storage segment (MountainWest). After February 2023, the businesses were managed withintwo reportable segments, our Natural Gas Distribution segment (Southwest Gas) and our Utility Infrastructure Services segment (Centuri) until August 2025, After August 2025, our business is solely comprised of our Natural Gas Distribution segment (see Note 16 - Segment Information).

Southwest Gas is engaged in the business of purchasing, distributing, and transporting natural gas for customers in portions of Arizona, Nevada, and California. Public utility rates, practices, facilities, and service territories of Southwest Gas are subject to regulatory oversight. The timing and amount of rate relief can materially impact results of operations. Natural gas purchases and the timing of related recoveries can materially impact liquidity. While mechanisms exist in all states in which Southwest Gas operates which decouple authorized operating cost recovery and profitability from the volume of natural gas sold, thereby also incentivizing energy conservation, results for the Natural Gas Distribution segment are higher during winter periods due to the seasonality incorporated in its regulatory rate structures.

In December 2022, the Company announced that its Board unanimously determined to take strategic actions to simplify the Company’s portfolio of businesses. These actions included entering into a definitive agreement to sell 100% of MountainWest in an all-cash transaction to Williams for $1.5 billion in total enterprise value, subject to certain adjustments. The sale closed on February 14, 2023.

Also as part of this simplification strategy, the Company previously communicated that it would pursue a separation of Centuri. In April 2024, the Company and Centuri announced the completion of the Centuri IPO. Following the Centuri IPO, the Company owned approximately 81% of Centuri. From May 2025 through September 2025, the Company completed a series of secondary public offerings and private placements of its holdings of Centuri common stock and, on September 5, 2025, completed a sale of its remaining shares. The Company’s sale of Centuri (which represents the entirety of the Company’s Utility Infrastructure Services segment) met the criteria to be presented as discontinued operations in accordance with U.S. GAAP. See Note 2 - Summary of Significant Accounting Policiesand Note 13 - Dispositions. After completion of the offering, the Company no longer owns any shares of Centuri common stock and no longer has governance rights afforded to it under the Separation Agreement including the right to nominate any of Centuri’s directors and any remaining consent rights over certain of Centuri’s corporate actions.

Note 2 - Summary of Significant Accounting Policies

Basis of Presentation. The Company follows U.S. GAAP in accounting for all of its businesses. Unless specified otherwise, all amounts are in U.S. dollars. Accounting for regulated operations conforms with U.S. GAAP as applied to rate-regulated companies and as prescribed by federal agencies and commissions of the various states in which the rate-regulated companies operate. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Certain items in the prior period financial statements have been reclassified to conform to the current year presentation. Such reclassifications did not affect revenue, operating income, net income, or total cash flows from operations, investing or financing activities. These include $74.3 million and $294.9 million of changes in accrued purchased gas costs, included in the changes in other current assets and liabilities, that were reclassified to changes in deferred purchased gas costs in the Company’s and Southwest’s consolidated statements of cash flows for the years ended December 31, 2024 and 2023, respectively. See Note 3 -Revision of Previously Issued Financial Statements for the discussion of the revision to the prior year financial statements.

Discontinued Operations. On August 11, 2025, the Company completed a secondary public offering and a concurrent private placement transaction with Icahn investment entities. These transactions resulted in the sale of a combined total of 18,823,500 shares of Centuri common stock previously held by the Company (see Note 13 - Dispositions). Following the completion of these transactions, the Company no longer maintained a controlling financial interest in Centuri. Accordingly, Centuri’s assets, liabilities, and results of operations are no longer included in the Company’s consolidated financial statements.

In addition, the sale of Centuri, which comprised the Company’s Utility Infrastructure Services segment, represented a strategic shift that had a significant impact on the Company’s operations and financial results. Therefore, Centuri met the criteria to be reported as discontinued operations in accordance with U.S. GAAP. The results of discontinued operations are aggregated and presented separately in the Consolidated Statements of Income and Consolidated Statements of Cash Flows for all periods presented. Assets and liabilities of the discontinued operations are aggregated and reported separately on the Consolidated Balance Sheets as of December 31, 2024. Unless otherwise noted, the financial disclosures and related information provided herein relate to our continuing operations, which exclude our former Utility Infrastructure Services segment, and we have recast prior period amounts to reflect discontinued operations.

Consolidation. The accompanying financial statements (as of and for the periods presented) are presented on a consolidated basis for the Company and Southwest Gas. All significant intercompany balances and transactions have been eliminated with the exception of transactions between Southwest Gas and Centuri in accordance with accounting treatment for rate-regulated entities.

Fair Value Measurements. Certain assets and liabilities are reported at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.

U.S. GAAP states that a fair value measurement should be based on the assumptions that market participants would use in pricing the asset or liability and establishes a fair value hierarchy that ranks the inputs used to measure fair value by their reliability. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to fair values derived from unobservable inputs (Level 3 measurements). Financial assets and liabilities are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. The three levels of the fair value hierarchy are as follows:

Level 1 – quoted prices (unadjusted) in active markets for identical assets or liabilities that a company has the ability to access at the measurement date.

Level 2 – inputs other than quoted prices included within Level 1 that are observable for similar assets or liabilities, either directly or indirectly.

Level 3 – unobservable inputs for the asset or liability. Unobservable inputs are used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date.

The Company primarily used quoted market prices and other observable market pricing information (exclusive of any purchase accounting adjustments) in valuing cash and cash equivalents, long-term debt outstanding, and assets of the qualified pension plan and the postretirement benefits other than pensions required to be recorded and/or disclosed at fair value. The Company uses prices and inputs that are current as of the measurement date and recognizes transfers between levels at either the actual date of an event or a change in circumstance that caused the transfer.

Net Regulated Operations Plant. Net regulated operations plant includes gas plant at original cost less the accumulated provision for depreciation and amortization plus any unamortized balance of acquisition adjustments. Original cost generally includes contracted services, material, payroll, and related costs such as taxes and certain benefits, general and administrative expenses applicable to construction efforts, and an allowance for funds used during construction less contributions in aid of construction. Aligned with regulatory treatment, when plant is retired the cost of such plant, net of any salvage value, is charged to accumulated depreciation. See also Depreciation and Amortization below.

Other Property and Investments. Other property and investments on Southwest Gas’ and the Company’s Consolidated Balance Sheets include:

Included in the table above are the net cash surrender values of COLI policies. These life insurance policies on members of management and other key employees are used by Southwest Gas to indemnify itself against the loss of talent, expertise, and knowledge, as well as to provide indirect funding for certain nonqualified benefit plans.

Cash and Cash Equivalents. For purposes of reporting consolidated cash flows, cash and cash equivalents include cash on hand, money market funds, and financial instruments with original maturities of three months or less. Such investments are carried at cost, which approximates fair value. Cash and cash equivalents of the Company include$250.5 million and$64.3 million of money market fund investments at December 31, 2025 and 2024, respectively. Of these amounts, $34.4 million and $48.8 million at December 31, 2025 and 2024, respectively, were held by Southwest Gas. The money market fund investments were acquired and are generally redeemable at their net asset value.

Income Taxes. The asset and liability method of accounting is utilized for the recognition of income taxes. Under the asset and liability method, deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred income tax assets and liabilities are measured using enacted income tax rates expected to apply to taxable income in the years in which those temporary differences are anticipated to be recovered or settled. The effect on deferred income tax assets and liabilities of a change in income tax rates is recognized in the period that includes the enactment date. For regulatory and financial reporting purposes, ITCs related to gas utility operations are deferred and amortized over the life of related fixed assets.

Deferred Purchased Gas Costs. The various regulatory commissions have established procedures to enable Southwest Gas to adjust billing rates for changes in the cost of natural gas purchased. The difference between the current cost of gas purchased and the cost of gas recovered in billed rates is deferred. Generally, these deferred amounts are recovered or refunded withinone year.

Materials, supplies, and gas inventories. Materials, supplies, and gas inventories for Southwest Gasand the Company includesgas pipe materials and operating supplies of $78.1 million and $77.8 million as of December 31, 2025 and 2024, respectively (carried at weighted average cost).

Prepaid and other current assets. Prepaid and other current assets for Southwest Gasand the Company include, among other things, $91.1 million and $32.4 million related to a regulatory asset associated with the Arizona decoupling mechanism as of December 31, 2025 and 2024, respectively. Additionally, included in the balance for the Company is prepaid insurance premiums of $35.4 million and $25.3 million as of December 31, 2025 and 2024, respectively, and $33.9 million and $25.2 million as of December 31, 2025 and 2024, respectively, at Southwest Gas.

Goodwill. As required by U.S. GAAP, goodwill is assessed for impairment annually or more frequently if circumstances indicate impairment to the carrying value of goodwill may have occurred. The goodwill impairment analysis was conducted as of October 1, 2025 using a qualitative assessment, as permitted by U.S. GAAP. Management of the Company and Southwest Gas evaluated its reporting unit and operating segment and concluded that, following the sale of the of the Utility Infrastructure Services segment (Centuri), the Company operates solely within the Natural Gas Distribution segment (Southwest Gas); see Note 16 - Segment Information. The Company and Southwest Gas determined that it is more likely than not that the fair value of Southwest Gas’ reporting unit exceeds their carrying amounts in both 2025 and 2024 and therefore no quantitative assessment was performed.

Deferred charges and other assets. Deferred charges and other assets for Southwest Gas and the Company include, among other things, cloud-based software of $33.9 million and $24.8 million as of December 31, 2025 and 2024, respectively, and a regulatory asset associated with pension for Arizona and Nevada of $246.4 million and $300.0 million as of December 31, 2025 and 2024, respectively. The change is due to the net actuarial gain (refer to Note 10 - Pension and Other Postretirement Benefits).

Noncontrolling Interest. In connection with the Centuri IPO, the Company recorded a noncontrolling interest as part of equity in the Consolidated Balance Sheet (associated with the interests held by the new investors in Centuri) and recognized the excess of the fair value of the Centuri IPO proceeds over the carrying value of the noncontrolling interest, in addition to a portion of AOCI relevant to the proportional interest of the noncontrolling parties in Centuri, within Additional paid-in capital. The Consolidated Statements of Income include multiple components of comprehensive income attributable to noncontrolling interests following the Centuri IPO. These amounts, including those distinguishable from net income attributed to these parties, are separately presented in the Consolidated Statements of Equity. Following the completion of the Centuri Separation (see Note 13 - Dispositions below), the Company no longer maintained a controlling financial interest in Centuri. Accordingly, the noncontrolling interests in Centuri are no longer included in the Company’s consolidated financial statements.

Redeemable Noncontrolling Interest. Separate from the noncontrolling ownership interest in Centuri, redeemable noncontrolling interests have been established in association with certain business acquisitions by Centuri. Following the completion of the Centuri Separation (see Note 13 - Dispositions below), the Company no longer maintained a controlling financial interest in Centuri. Accordingly, the redeemable noncontrolling interests in Centuri are no longer included in the Company’s consolidated financial statements.

Other Current Liabilities. Management recognizes in its balance sheets various liabilities that are expected to be settled through future cash payments within the next twelve months, including certain regulatory mechanisms (refer to Note 5 - Regulatory Assets and Liabilities), customary accrued expenses for employee compensation and benefits, declared but unpaid dividends, and miscellaneous other accrued liabilities.

Accumulated Removal Costs. Approved regulatory practices allow Southwest Gas to include in depreciation expense a component intended to recover removal costs associated with regulated operations plant retirements. In accordance with the SEC position on presentation of these amounts, management reclassifies estimated removal costs from Accumulated depreciation to Accumulated removal costs within the liabilities section of the Consolidated Balance Sheets. Management regularly updates the estimated accumulated removal costs as amounts fluctuate between periods depending on the level of replacement work performed (and actual cost experience) compared to the estimated cost of removal in rates.

Revenue. See Note 6 - Revenue for information related to revenue recognition for Southwest Gas.

Intercompany Transactions. Centuri recognizes revenues generated from contracts with Southwest Gas (see Note 16 - Segment Information). The accounts receivable balance, revenues, and associated profits were included in the consolidated financial statements of the Company and Southwest Gas and were not eliminated during consolidation in accordance with accounting treatment for rate-regulated entities through the period prior to deconsolidation (see Note 13 - Dispositions).

Net Cost of Gas Sold. Components of net cost of gas sold include natural gas commodity costs (fixed-price and variable-rate), pipeline capacity/transportation costs, and any actual settled costs of natural gas derivative instruments, where relevant. Also included are the net impacts of PGA deferrals and recoveries which by their inclusion result in net cost of gas sold overall that is comparable to amounts included in billed gas operating revenues. Differences between amounts incurred with suppliers, transmission pipelines, etc. and amounts already included in customer rates are temporarily deferred in PGA accounts pending inclusion in customer rates.

Operations and Maintenance Expense. Operations and maintenance expense includes, Southwest Gas’ operating and maintenance costs associated with serving utility customers and maintaining its distribution and transmission systems, uncollectible customer accounts expense, administrative and general salaries and expense, and employee benefits expense excluding relevant non-service cost components (that have been reclassified to Other income (deductions) due to requirements in U.S. GAAP), as well as legal expenses (including injuries and damages), professional and other external contracted services, and other business expenses.

Depreciation and Amortization. Regulated operations plant depreciation is computed on the straight-line remaining life method at composite rates considered sufficient to amortize costs over estimated service lives, including components which compensate for removal costs (net of salvage value), and retirements, as approved by the appropriate regulatory agency. When plant is retired from service, the original cost of plant, including cost of removal, less salvage, is charged to the accumulated provision for depreciation. See also discussion regarding Accumulated Removal Costs above. Other regulatory assets, including acquisition adjustments, are amortized, when appropriate, over time periods authorized by regulators. Costs and gains related to refunding regulated operations debt and debt issuance expenses are deferred and amortized over the weighted-average lives of the new issues and become a component of interest expense.

AFUDC. AFUDC represents the cost of both debt and equity funds used to finance regulated operations plant construction. AFUDC is capitalized as part of the cost of regulated operations plant. The debt portion of AFUDC is reported in the Company’s and Southwest Gas’ Consolidated Statements of Income as an offset to Net interest deductions and the equity portion is reported as Other income. Regulated operations plant construction costs, including AFUDC, are recoverable as part of authorized rates through depreciation when completed projects are placed into operation and general rate relief is requested and granted. AFUDC, disaggregated by type, included in the Company’s and Southwest Gas’ Consolidated Statements of Income are presented in the table below:

(1)Equity AFUDC for the year ended December 31, 2023 includes MountainWest activity.

Debt and equity AFUDC at Southwest Gas were impacted in 2023 by the amount of short-term debt outstanding based on the regulatory formula for each component.

Other Income (Deductions). The following table provides the composition of significant items included in Other income (deductions) on the Consolidated Statements of Income:

Included in the table above is the change in COLI policies (including net death benefits recognized, where relevant). Current tax regulations provide for tax-free treatment of life insurance (death benefit) proceeds. Therefore, changes in the cash surrender value components of COLI policies, as they progress towards the ultimate death benefits, are also recorded without tax consequences.

For 2025, interest income relates to interest income earned on money market investments and interest income earned on Southwest Gas’ regulatory asset balances, including the Arizona decoupling mechanism. For 2023 and 2024, interest income primarily relates to Southwest Gas’ regulatory asset balances, including its deferred purchased gas cost mechanisms, the combined balance of which was a net asset balance of $465.3 million as of December 31, 2023 and transitioned to a net liability balance of $241.6 million as of December 31, 2024. Interest income is earned on asset balances and interest expense is incurred on liability balances. Interest earned on money market accounts, as discussed in the cash and cash equivalent section above, also contributes to interest income. In regard to net periodic benefit cost, refer to Note 10 - Pension and Other Postretirement Benefits. Miscellaneous expense for Southwest Gas between years includes a variety of items, not limited to, but including where applicable, write-offs for uncompleted software projects and the reduction in value of Southwest Gas’ previous corporate campus property.

Derivatives. In managing its natural gas supply portfolios, Southwest Gas has historically entered into fixed- and variable-price contracts, which qualify as derivatives. The fixed-price contracts, firm commitments to purchase a fixed amount of gas in the future at a fixed price, qualify for the normal purchases and normal sales exception that is allowed for contracts that are probable of delivery in the normal course of business and are exempt from fair value reporting. The variable‑price contracts meet the definition of derivative financial instruments; however, because the contract price is set at the prevailing market price on the future transaction date, no mark‑to‑market adjustment is required. Southwest Gas does not utilize derivative financial instruments for speculative purposes, nor does it have trading operations.

EPS. Basic EPS in each period of this report were calculated by dividing net income (loss) attributable to the Company by the weighted-average number of shares during those periods. Diluted EPS includes additional weighted-average common stock equivalents (performance share units and restricted stock units), if dilutive. Unless otherwise noted, the term EPS refers to Basic EPS. A reconciliation of the denominator used in Basic and Diluted EPS calculations is shown in the following table:

(1) The number of securities granted for 2025, 2024, and 2023 includes 146,000,158,000, and 173,000 performance stock units, respectively, the total of which was derived by assuming that target performance will be achieved during the relevant performance period.

(2) The number of anti-dilutive restricted stock units excluded from the calculation of diluted shares from discontinued operations in 2024 is 191,000.

Recent Accounting Standards Updates.

Recently issued accounting pronouncement adopted in 2025:

In December 2023, the FASB issued ASU 2023-09 “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” The update, among other amendments, provides for additional disclosure requirements related to the effective income tax rate reconciliation and income taxes paid. Under the revised guidance for the effective income tax reconciliations, entities would be required to disclose: (1) eight specific categories in the effective income tax rate reconciliation in both percentages and reporting currency amount, (2) additional information for reconciling items over a certain threshold, (3) explanation of individual reconciling items disclosed, and (4) provide a qualitative description of the state and local jurisdictions that contribute to the majority of the state income tax expense. For each annual period presented, the new standard requires disclosure of the year-to-date amount of income taxes paid (net of refunds received) disaggregated by federal, state, and foreign. It also requires additional disaggregated information on income taxes paid (net of refunds received) to an individual jurisdiction equal to or greater than 5% of total income taxes paid (net of refunds received). The standard is effective for annual periods beginning January 1, 2025. The Company and Southwest Gas have retrospectively adopted this update in the fourth quarter of 2025, the impact of which is reflected in Note 11 - Income Taxes, with no impact on results of operations, cash flows, or financial condition of the Company or Southwest Gas.

In July 2025, the FASB issued ASU 2025-05 “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets.” The amendments in this update provide a practical expedient permitting an entity to assume that conditions at the balance sheet date remain unchanged over the life of the asset when estimating expected credit losses for current accounts receivable and current contract assets. The update is effective for annual periods beginning after December 15, 2025; early adoption is permitted. Management adopted ASU 2025-05 beginning with the fourth quarter of fiscal 2025 and utilized the practical expedient provided therein. The adoption of this ASU did not have a material impact on the Company’s or Southwest Gas’ financial position or results of operations.

Recently issued accounting pronouncements that will be effective in 2026 and thereafter:

In November 2024, the FASB issued ASU 2024-03 “Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses.” The update requires disclosure of disaggregated information about certain income statement expense line items in the notes to the financial statements. The update is effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027; early adoption is permitted. The update should be applied prospectively; however, retrospective application is also permitted. Management is evaluating the impacts this update might have on the Company’s and Southwest Gas’ disclosures.

In September 2025, the FASB issued ASU 2025-06 “Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software.” The amendments in this update improve the operability of the guidance by removing all references to software development project stages so that the guidance is neutral to different software development methods. This update is effective for annual periods beginning after December 15, 2027, including interim periods within those fiscal years; early adoption is permitted. Management is evaluating the impacts this update might have on the Company’s and Southwest Gas’ consolidated financial statements.

Subsequent Events. Management monitors events occurring after the balance sheet date and prior to the issuance of the financial statements to determine the impacts, if any, of events on the financial statements to be issued or disclosures to be made and has reflected them where appropriate.

Note 3 -Revision of Previously Issued Financial Statements

In connection with the preparation of the Company’s 2025 Form 10-K for Southwest Gas, management identified errors in the calculation of the estimated deferred income tax liabilities associated with state income taxes. The issues result from not timely updating estimated apportionment rates to reflect certain events. For Southwest Gas, the errors date back to the formation of Southwest Gas Holdings in 2017, when Southwest Gas and Centuri became wholly-owned subsidiaries of Southwest Gas Holdings. These errors were determined to be not material to any previously issued Southwest Gas financial statements. However, Southwest Gas revised the historical financial statements due to the magnitude of the cumulative effect of the prior year errors. Southwest Gas also revised the historical financial statements to correct other previously identified immaterial errors.

The effects of the correction of the errors on the Consolidated Financial Statements are as follows:

Note 4 - Regulated Operations Plant

Net Regulated Operations Plant

Major classes of regulated operations plant and their respective balancesas of December 31, 2025 and 2024 were as follows:

Regulated operations plant depreciation is computed on the straight-line remaining life method at composite rates considered sufficient to amortize costs over estimated service lives, including components which are intended to compensate for removal costs (net of salvage value), and retirements, based on the processes of regulatory proceedings and related regulatory commission approvals and/or mandates. In 2025, annual regulated operations depreciation and amortization expense in regard to Southwest Gas averaged 2.7% of the original cost of depreciable and amortizable property, and 2.6% in 2024 and 2023. Transmission and distribution plant are associated with the core natural gas delivery infrastructure, and combined, constitute the majority of gas plant. Annual regulated operations depreciation expense for Southwest Gas averaged approximately 2.3% of the original cost of depreciable transmission and distribution plant during the period 2023 through 2025.

Depreciation and amortization expense on gas plant was as follows:

Leases

Determinations are made as to whether an arrangement is a lease at inception. ROU assets represent the right to use an underlying asset for the lease term; lease liabilities represent obligations to make lease payments arising from the lease. Operating lease ROU assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. When leases do not provide an implicit interest rate, an incremental borrowing rate based on information available at commencement is used in determining the present value of lease payments; an implicit rate, if readily determinable, is used. Lease terms utilized in the computations may include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. When lease agreements include non-lease components, they are included with the lease component and accounted for as a single component, for all asset classes. Southwest Gas has no significant operating, finance, or short-term leases.

Note 5 - Regulatory Assets and Liabilities

Southwest Gas is subject to the regulation of the ACC, the PUCN, the CPUC, and the FERC. Accounting policies for Southwest Gas conform to U.S. GAAP applicable to rate-regulated entities and reflect the effects of the ratemaking process. Accounting treatment for rate-regulated entities allows for deferral as regulatory assets, costs that otherwise would be expensed, if it is probable that future recovery from customers will occur. If rate recovery is no longer probable, due to competition or the actions of regulators, the related regulatory asset is required to be written off. Regulatory liabilities are recorded if it is probable that revenues will be reduced for amounts that will be refunded to customers through the ratemaking process. Management records regulatory assets and liabilities based on decisions of the commissions noted above, including the issuance of regulatory orders and precedents established by these commissions. Southwest Gas has generally been successful in seeking recovery of regulatory assets and regularly files rate cases or other administrative filings in the various jurisdictions, in some cases, to establish the basis for recovering regulatory assets reflected in accounting records.

The following table represents existing regulatory assets and liabilities. The amounts reported in the table below differ from Southwest Gas due to the revision Note 3 -Revision of Previously Issued Financial Statements.

(1) Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovery period is greater than five years. (See Note 10 - Pension and Other Postretirement Benefits).

(2)Balance recovered or refunded on an ongoing basis with interest.

(3) Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovered over life of debt instruments.

(4)Recovery through cost of service generally on aone-year lag basis and part of overhead loading processes. Included in Prepaid and other current assets on the Consolidated Balance Sheets.

(5)Margin tracking/decoupling mechanisms are alternative revenue programs; revenue associated with under-collections (for the difference between authorized margin levels and amounts billed to customers through rates currently) is recognized as revenue so long as recovery is expected to take place within 24 months. The property tax tracking mechanism reflects differences in property tax expense and the amount included in the current general rate case. Total category asset balances are included in Prepaid and other current assets and Deferred charges and other assets on the Consolidated Balance Sheets. For 2025, total category liability balances are included in Other deferred credits and other long-term liabilities. For 2024, total category liability balances are included in Other current liabilities and Other deferred credits and other long-term liabilities.

(6) Included in Accumulated removal costs on the Consolidated Balance Sheets; a component of ongoing depreciation rates as part of margin rates overall and of benchmarks under trackers as part of general rate cases.

(7) Included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets; amortized over life of debt instruments.

(8) Includes remeasurement/reduction of the net accumulated deferred income tax liability from U.S. tax reform. The reduction (EADIT) became a regulatory liability with tax gross-up. EADIT reduces rate base, and is expected to be returned to utility customers in accordance with IRS and regulatory requirements. Included generally in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets, except for $10.0 million in 2025 and $21.0 million in 2024, which is in Other current liabilities.

(9) The following tables detail the components of Other regulatory assets and liabilities. Other regulatory assets are included in either Prepaid and other current assets or Deferred charges and other assets on the Consolidated Balance Sheets (as indicated). Recovery periods vary. Other regulatory liabilities are included in either Other current liabilities or Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets (as indicated).

(10) Deferred purchased gas costs as of December 31, 2024 differs from Southwest Gas due to the revision discussed in Note 3 -Revision of Previously Issued Financial Statements.

(11) Net regulatory assets (liabilities) for the year ended December 31, 2024 differs from Southwest Gas due to the revision discussed in Note 3 -Revision of Previously Issued Financial Statements.

(a) Included in Prepaid and other current assets on the Consolidated Balance Sheets.

(b) Included in Deferred charges and other assets on the Consolidated Balance Sheets.

(c) In 2025, approximately $5.5 million of these balances included in Prepaid and other current assets and $1.6 million in Deferred charges and other assets on the Consolidated Balance Sheets. In 2024, approximately $2.6 million included in Prepaid and other current assets and $1.1 million included in Deferred charges and other assets on the Consolidated Balance Sheets.

(d) Included in Deferred charges and other assets on the Consolidated Balance Sheets.

(e) In 2025, approximately$7.6 million included in Prepaid and other current assets and $7.6 million included in Deferred charges and other assets on the Consolidated Balance Sheets. In 2024, $11.7 million included in Prepaid and other current assets and $9.9 million included in Deferred charges and other assets on the Consolidated Balance Sheets.

(f) Balance recovered or refunded on an ongoing basis, generally with interest.

(g) Included in Other current liabilities on the Consolidated Balance Sheets.

(h) Balance typically recovered or refunded on an ongoing basis, generally with interest.

(i) Included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets.

Regulatory Assets/Liabilities Not Earning a Return

•Regulatory assets/liabilities related to accrued pension and other postretirement benefit costs are offset by corresponding liabilities/assets. The assets are recovered in rates as the plans are funded.

•Margin-related mechanisms exist in various forms in each of the Company’s regulatory jurisdictions. Balances related to the decoupling mechanisms in Nevada do not earn a return. Recovery rates are designed to recover the outstanding balances over atwelve-month period.

Regulatory Assets/Liabilities Earning a Return

•Over- and undercollected regulatory balancing accounts and other regulatory assets, net, reflect the difference between customer billings and recorded or authorized by the ACC, CPUC, PUCN, or FERC. Depreciation, taxes and return on rate base may also be included in certain accounts. Amounts in the balancing accounts are recoverable (receivable) or refundable (payable) in future rates, subject to ACC, CPUC, PUCN, or FERC approval. These relate to the following:

▪The following mechanisms earn a return on based on the monthly one-year nominal Treasury Constant Maturities for Arizona and Commercial Paper for California and are generally designed to address the outstanding balances over atwelve-month period:

•Deferred purchased gas cost

•Margin-related mechanisms

•State mandated public purpose programs

▪The following mechanisms are revenue requirement and earn the authorized rate of return per the general rate cases for the applicable jurisdiction:

•Deferred purchased gas cost - Nevada

•Unamortized premium on reacquired debt

•Accrued absence time

•Interest-tracking mechanism

•Property tax-tracking mechanisms

•Accumulated removal costs

•Unamortized gain on reacquired debt

•Regulatory excess deferred/other taxes and gross-up mechanism

•Pension tracking mechanism

▪Infrastructure replacement programs vary by jurisdiction and program type.

Note 6 - Revenue

Southwest Gas recognizes revenue when it satisfies its performance by transferring gas to the customer. Revenues also include the net impacts of margin tracker and decoupling accruals based on criteria in U.S. GAAP for rate-regulated entities associated with alternative revenue programs. Revenues from customer arrangements and from alternative revenue programs are described below.

Southwest Gas acts as an agent for state and local taxing authorities in the collection and remittance of a variety of taxes, including sales and use taxes and surcharges. These taxes are not included in Regulated operations revenues. Management uses the net classification method to report taxes collected from customers to be remitted to governmental authorities.

Southwest Gas generally offerstwo types of services to its customers: tariff sales and transportation–only service. Tariff sales encompass sales to primarily residential and small commercial customers under various rate schedules, subject to cost-of-service ratemaking, which is based on the rate-regulation of the ACC, CPUC, PUCN, and FERC. Southwest Gas provides both the commodity and the related distribution service to nearly all of its approximate 2.3 million customers, and only several hundred customers subscribe to transportation-only service. Natural gas is delivered and consumed by the customer simultaneously. The provision of service is represented by the turn of the meter dial and is the primary representation of the satisfaction of all performance obligations required for Southwest Gas to recognize revenue. The amount billable via regulated rates, billed via both volumetric and fixed monthly rates as part of rate design, corresponds to the value to the customer, and Southwest Gas believes that the amount billable is appropriate to utilize for purposes of recognizing revenue. Estimated amounts remaining unbilled since the last meter read date are also recognized for service provided through the balance sheet date. While natural gas service is typically recurring, there is generally not a contract term for utility service. Therefore, the contract term is not generally viewed to extend beyond the service provided to date and customers are able to generally terminate service at will.

Transportation-only service is also governed by tariff rate provisions. Transportation-only service is generally only available to large customers under requirements of Southwest Gas’ various tariffs. With this service, customers secure their own gas supply and Southwest Gas provides transportation services to move the customer-supplied gas to the intended location. Southwest Gas recognizes transportation service revenue over time through a combination of volumetric charges and fixed charges through a variety of design mechanisms approved by regulators. These types of fixed charges represent a separate performance obligation associated with standing ready over the period of the month to deliver quantities of gas regardless of whether the customer takes delivery of any quantity of gas. The performance obligations under these circumstances are satisfied over the course of the month under an output measure of progress based on time, which correlates to the period for which the charges are eligible to be invoiced.

Under its regulations, Southwest Gas enters into negotiated-rate contracts with customers located near competing pipelines that pose a risk of bypassing its distribution system. Southwest Gas may also enter into similar contracts for customers that are otherwise able to satisfy their energy needs through a fuel alternative to natural gas. Less thantwo dozen customers are party to contracts with rate components subject to negotiation. Many rate provisions and terms of service for these less common types of contracts are also subject to regulatory oversight and tariff provisions. The performance obligations for these customers are satisfied similarly to those for other customers by means of transporting and delivering natural gas to the customer. Many or most of the rate components and structures for these types of customers are the same as those for similar customers that do not have without negotiated rate components and the negotiated rates are within the parameters of the tariff guidelines. Furthermore, while some of these contracts may include multi-year contract periods because amounts billable under the contract are based on rates in effect for the customer for service provided to date, no significant financing component is believed to exist.

As indicated above, revenues also include the net impacts of margin tracker and decoupling accruals. All of Southwest Gas’ service territories have decoupled rate structures that are designed to eliminate the direct link between volumetric sales and revenue, thereby mitigating the impacts of unusual weather variability and conservation on margin. These decoupled rate structures qualify as alternative revenue programs. The primary alternative revenue programs involve adjustments for differences between stated tariff benchmarks and amounts billed through revenue from contracts with customers via existing rates. Such adjustments are recognized monthly in revenue and in the associated regulatory asset or liability accounts in advance of rate adjustments intended to collect or return the amounts recognized. Revenues recognized for the adjustment to the benchmarks noted are required to be presented separately from revenues from contracts with customers, as such, these revenues are disaggregated in the table below as Alternative revenue program revenues.

Southwest Gas’ operating revenues, but not its operating margin, are directly impacted by variability between comparative periods in the cost of natural gas procured for customers as these costs are incorporated in customer rates. When included in rates (for customers except those taking transportation-only service), these costs are passed through to customers generally dollar-for-dollar without markup. Operating margin is a non-GAAP financial measure and should be considered in addition to, not as a substitute for, measures of financial performance prepared in accordance with GAAP. Southwest Gas’ revenues overall, reflected on the Consolidated Statements of Income of both the Company and Southwest Gas, include revenue from contracts with customers, which is shown below disaggregated by customer type, in addition to other categories of revenue:

(1) Amounts include late fees and other miscellaneous revenues and may also include the impact of certain regulatory mechanisms.

(2) The amounts differ from Southwest Gas due to the revision discussed in Note 3 - Revision of Previously Issued Financial Statements.

(3) The Company’s Total Regulated operations revenues differ from Southwest Gas due to the revision discussed in Note 3 - Revision of Previously Issued Financial Statements.

(4) The Company’s revenues for the period ended December 31, 2023 represent the amounts for the Natural Gas Distribution segment and do not include amounts attributable to MountainWest. As these amounts are not material, management has not provided disaggregated revenue disclosures.

As of December 31, 2025, the Company and Southwest had backlog performance obligations through Great Basin, excluding intercompany transactions, totaling $58.2 million for the next four years. Of the current backlog, $15.9 million is expected to be fulfilled within the year ended December 31, 2026. $15.9 million within the year ended December 31, 2027, $15.9 million within the year ended December 31, 2028, and $10.5 million within the year ended December 31, 2029. Under the terms of Great Basin’s current settlement agreement, new rates will become effective no later than September 1, 2029. Accordingly, the Company and Southwest Gas are unable to reasonably estimate performance obligations that may arise beyond September 1, 2029. The backlog consists of firm customer contracts for natural gas distribution services. Seasonal fluctuation may impact the timing of fulfillment as demand for natural gas typically increases during winter months. The Company defines backlog as the aggregate value of signed contracts for which performance obligations remain unsatisfied.

Note 7 - Receivables and Related Allowances

Business activity with respect to natural gas utility operations is conducted with customers located within thethree-state region of Arizona, Nevada, and California. Southwest Gas’ accounts receivable are short-term in nature with billing due dates customarily not extending beyondone month. Customers’ credit worthiness is assessed upon account creation by evaluation of other utility service or their credit file and related payment history. Although Southwest Gas seeks to minimize its credit risk related to utility operations by requiring security deposits from new customers, imposing late fees, and actively pursuing collection on overdue accounts where possible, some accounts are ultimately not collected. Customer accounts are subject to collection procedures that vary by jurisdiction, such as late fee assessment, notice requirements for disconnection of service, and procedures for actual disconnection and/or reestablishment of service. After disconnection of service, accounts are customarily written off approximatelytwo months after disconnection if the account remains inactive. Depending upon the jurisdiction, reestablishment of service requires both the payment of previously unpaid balances and additional deposit requirements. Generally, costs related to uncollectible accounts are included in the ratemaking process as a cost of service. However, the Nevada and California jurisdictions have certain regulatory mechanisms in place to separately track and collect portions of uncollectible accounts through the mechanisms. Eligible amounts are deferred and collected through a surcharge in the ratemaking process. Southwest Gascontinues to actively work with customers experiencing financial hardship by means of flexible payment options and partnering with assistance agencies. Provisions for uncollectible accounts are recorded monthly based on each customer’s current ability to pay amounts that are due, payment history, consideration of current conditions, customer and rate composition, regulatory requirements, and write-off processes.

The table below contains information about Southwest Gas’ gas utility customer accounts receivable balance (net of allowance) at December 31, 2025 and 2024:

The following table represents the percentage of customers in each of Southwest Gas’three states at December 31, 2025, which was consistent with the prior year:

Southwest Gas activity in the allowance account for uncollectibles is summarized as follows:

The table above does not provide the effect for amounts included in the regulatory tracking mechanisms noted earlier.

Note 8 - Common Stock

Shares of the Company’s common stock are publicly traded on the NYSE under the ticker symbol “SWX.” Share-based compensation related to Southwest Gas is based on awards to be issued in shares of the Company.

In November 2023, the Company and Southwest Gas jointly filed an automatic shelf registration statement (File No. 333-275774), or a Universal Shelf, which became effective upon filing and includes a prospectus detailing the Company’s ability to offer and sell, from time to time in amounts at prices and on terms that will be determined at the time of such offering, any combination of common stock, preferred stock, debt securities (which may or may not be guaranteed by one or more of its directly or indirectly wholly owned subsidiaries if indicated in the relevant prospectus supplement), guarantees of debt securities issued by Southwest Gas, depository shares, warrants to purchase common stock, preferred stock or depository shares issued by the Company or debt securities issued by the Company or Southwest Gas, units and rights. Additionally, as part of the Universal Shelf, Southwest Gas may offer and sell, from time to time in amounts at prices and on terms that will be determined at the time of such offering, any combination of debt securities (which may or may not be guaranteed by one or more of its directly or indirectly wholly owned subsidiaries if indicated in the relevant prospectus supplement) and guarantees of debt securities issued by the Company or by one or more of its directly or indirectly wholly owned subsidiaries, if indicated in the relevant prospectus supplement. The Universal Shelf is set to expire in November 2026.

On August 6, 2024, the Company entered into an Equity Distribution Agreement with J.P. Morgan Securities LLC and Wells Fargo Securities, LLC for the offer and sale of up to 340,000,000 of common stock from time to time in an ATM Program. The offering amount was carried forward from the Company’s previous at-the-market equity offering program. The shares are issuable pursuant to the Company’s Universal Shelf. No issuances have occurred under the ATM Program as of December 31, 2025.

During 2025, the Company issued approximately 186,000 shares of common stock through the omnibus incentive plan and restricted stock/unit plan.

During 2025, the Company issued 256,000 shares of common stock through the Dividend Reinvestment and Stock Purchase Plan, raising proceeds of approximately $19.2 million.

As of December 31, 2025, there were 5.0 million shares of common stock registered and available for issuance under the provisions of the various stock issuance plans.

Note 9 - Debt

Long-Term Debt

Long-term debt is recognized in the Company’s and Southwest Gas’ Consolidated Balance Sheets generally at the carrying value of the obligations outstanding. Details surrounding the fair value and individual carrying values of instruments are provided in the table that follows.

The fair values of the Company’s revolving credit facilities and IDRBs are estimated using observable market inputs, including current interest rates and are therefore classified as Level 2 in the hierarchy. The fair values of Southwest Gas’ debentures (which include senior and medium-term notes)were determined utilizing a market-based valuation approach, where fair values are determined based on observable trading data and as such are categorized as Level 2 in the hierarchy.

Southwest Gas has a $400.0 million credit facility scheduled to expire in August 2029. Southwest Gas designates $150.0 million of associated capacity as long-term debt and the remaining $250.0 million for working capital purposes. In June 2025, Southwest Gas amended this revolving credit agreement, which, among other things, added a swingline loan sub-facility in an aggregate principal amount at any time outstanding not to exceed $30.0 million and added a one-week interest period option with an interest rate equal to Daily Simple SOFR plus 0.03839% plus the applicable margin. At December 31, 2025, the applicable margin was 1.125% for loans bearing interest with reference to SOFR and 0.125% for loans bearing interest with reference to the alternative base rate. Southwest Gas is also required to pay a commitment fee on the unfunded portion of the commitments which ranges from 0.075% to 0.200%. At December 31, 2025, no borrowings were outstanding on the long-term portion (including under the commercial paper program discussed below) nor under the short-term portion of the facility.

Southwest Gas has a $50.0 million commercial paper program. Issuances under the commercial paper program are supported by Southwest Gas’ current revolving credit facility and therefore do not represent additional borrowing capacity. Borrowings under the commercial paper program, if any, are designated as long-term debt. Interest rates for the program are calculated at the then current commercial paper rate. At December 31, 2025, no borrowings were outstanding under the commercial paper program.

The effective interest rates on Southwest Gas’ variable-rate IDRBs are included in the table below:

In Nevada, interest fluctuations due to changing interest rates on Southwest Gas’ 2003 Series A, 2008 Series A, and 2009 Series A variable-rate IDRBs are tracked and recovered from customers through a variable interest expense recovery mechanism.

None of Southwest Gas’ debt instruments have credit triggers or other clauses that result in default if bond ratings are lowered by rating agencies. Interest and fees on certain debt instruments are subject to adjustment depending on Southwest Gas’ bond ratings. Certain debt instruments are subject to a leverage ratio cap, and the 6.1% Notes due 2041 are also subject to a minimum net worth requirement. At December 31, 2025, Southwest Gas was in compliance with all of its covenants. Under the most restrictive of the financial covenants, approximately $4.7 billion in additional debt could be issued while still meeting the leverage ratio requirement. Relating to the minimum net worth requirement, as of December 31, 2025, there is approximately $3.0 billion of cushion in equity. No specific dividend restrictions exist under the collective covenants. None of the debt instruments contain material adverse change clauses.

Estimated maturities of long-term debt and the current portion of long-term debt for the next five years are:

Short-Term Debt

In June 2025, Southwest Gas Holdings entered into a new $300.0 million revolving credit agreement that matures in August 2029 and replaced Southwest Gas Holdings’ existing $300.0 million credit facility that was set to expire in December 2026. At December 31, 2025, the applicable margin is 1.125% for loans bearing interest with reference to SOFR and 0.125% for loans bearing interest with reference to the alternative base rate. Southwest Gas Holdings has a one-week interest period option with an interest rate equal to Daily Simple SOFR plus 0.03839% plus the applicable margin. Southwest Gas Holdings is also required to pay a commitment fee on the unfunded portion of the commitments which ranges from 0.075% to 0.200%. The revolving credit agreement also contains a swingline loan sub-facility in an aggregate principal amount at any time outstanding not to exceed $30.0 million. At December 31, 2025, there wereno borrowing outstanding under this credit facility.

Southwest Gas Holdings has a $550.0 million term loan that had been set to mature in June 2026. Prior to the execution of the amendment, Southwest Holdings prepaid a portion of the indebtedness, decreasing the balance from $550.0 million to $225.0 million, utilizing proceeds received from the Centuri separation transactions. In August 2025, Southwest Gas Holdings paid the remaining balance of $225.0 million utilizing proceeds received from additional Centuri separation transactions. See Note 13 - Dispositions.

As indicated above in the Long-Term debt table, the 8% Series debenture for $75.0 million matures in August 2026.

The weighted average effective interest rate of all short-term borrowings is 9.23% at December 31, 2025. There wereno short-term borrowings at December 31, 2024.

Note 10 - Pension and Other Postretirement Benefits

Employees’ Investment Plan

An EIP is offered to eligible employees of Southwest Gas through deduction of a percentage of base compensation, subject to IRS limitations. The EIP provides for purchases of various mutual fund investments and Company common stock. For employees hired on or before December 31, 2021, one-half of amounts deferred are matched up to a maximum matching contribution of 3.5% of an employee’s annual compensation. Employees hired on or after January 1, 2022, are eligible for non-elective employer contributions of 3% plus a matching contribution (dollar-for-dollar) up to 7% of eligible compensation. Officers hired after January 1, 2022, are similarly eligible for non-elective and matching contributions. Contributions to the plan by Southwest Gas were $12.2 million, $9.9 million, and$8.3 million for 2025, 2024, and 2023, respectively.

Deferred Compensation Plan

A deferred compensation plan is offered to all officers of Southwest Gas, regardless of hire date, and a separate deferred compensation plan is offered to members of the Company’s Board. The plans provide the opportunity to defer up to 100% of annual cash compensation. One-half of amounts deferred by officers are matched up to a maximum matching contribution of 3.5% of an officer’s annual base salary. Upon retirement, payments of compensation deferred, plus interest, are made in equal monthly installments over 10,15, or 20 years, as elected by the participant. Directors have an additional option to receive such payments over afive-year period. Deferred compensation earns interest at a rate determined each January. The interest rate equals 150% of Moody’s Seasoned Corporate Bond Rate Index.

Pension and Postretirement Plans

A noncontributory QRP with defined benefits covering substantially all Southwest Gas employees hired on or before December 31, 2021, is available, in addition to a separate unfunded SERP, which is limited to Southwest Gas’ officers. PBOP are provided to qualified retirees for limited benefits related to health care, dental, vision and life insurance, some of which were subject to earlier “sunset” dates. The defined benefit QRP, SERP, and PBOP are not available to Southwest Gas employees hired on or after January 1, 2022. As noted above, employees hired on or after that date, are eligible for enhanced contributions to the EIP.

The overfunded or underfunded positions of defined benefit postretirement plans, including pension plans, are recognized in the Consolidated Balance Sheets. Any actuarial gains and losses, prior service costs, and transition assets or obligations are recognized in AOCI under Stockholders’ equity, net of tax, until they are amortized as a component of net periodic benefit cost.

A regulatory asset has been established for the portion of the total amounts otherwise chargeable to AOCI that are expected to be recovered through rates in future periods. Changes in actuarial gains and losses and prior service costs pertaining to the regulatory asset will be recognized as an adjustment to the regulatory asset account as these amounts are amortized and recognized as components of net periodic pension costs each year.

The QRP invests the majority of its plan assets in common collective trusts, which include a well-diversified portfolio of domestic and international equity securities and fixed income securities and are managed by a professional investment manager appointed by Southwest Gas. The investment manager has full discretionary authority to direct the investment of plan assets held in trust within the specific guidelines prescribed by Southwest Gas through the plan’s investment policy statement. Southwest Gas previously implemented an LDI strategy for part of the portfolio; a form of investing designed to better match the movement in pension plan assets with the impact of interest rate changes and, indirectly, inflation assumption changes on the pension plan liability. The implementation of the LDI strategy was intended to be phased in over time by using a glide path. The glide path was designed to increase the allocation of the plan’s assets to fixed income securities, as the funded status of the plan increases, in order to more closely match the duration of the plan assets to that of the plan liability. During the third quarter of 2025, the asset mix was adapted in accordance with an updated policy statement an allocation of approximately 45% equity securities and 55% fixed income securities with an estimated target hedge ratio of 95%. Beginning in 2024, a treasury futures overlay was added as part of the LDI strategy intending to manage interest rate fluctuations with the goal of reducing funded ratio volatility; as of the end of 2025, the pension plan was approximately 102% funded. While the overlay is intended for these purposes, there is no guarantee that these intentions will be achieved. Pension plan assets are held in a Master Trust. The pension plan funding policy is in compliance with the federal government’s funding requirements.

Pension costs for these plans are affected by the amount and timing of cash contributions to the plans, the return on plan assets, discount rates, and by employee demographics, including age, compensation, and length of service. Changes made to the provisions of the plans may also impact current and future pension costs. Actuarial formulas are used in the determination of pension costs and are affected by actual plan experience and assumptions about future experience. Key actuarial assumptions include the expected return on plan assets, the discount rate used in determining the projected benefit obligation and pension costs, and the assumed rate of increase in employee compensation. Relatively small changes in these assumptions, particularly the discount rate, may significantly affect pension costs and plan obligations for the QRP. In determining the discount rate, management matches the plan’s projected cash flows to a spot-rate yield curve based on highly rated corporate bonds.

The asset return assumption (which impacts the following year’s expense) remained consistent with the prior year. The rates are presented in the table below:

Future years’ expense level movements (up or down) may continue to be greatly influenced by long-term interest rates, asset returns, and funding levels; however, management implemented a treasury futures overlay to primarily be responsive to changing interest rates, and therefore, indirectly, discount rates that will apply to the pension, in attempting to preserve funded status.

The following table sets forth the QRP, SERP, and PBOP funded statuses and amounts recognized on the Consolidated Balance Sheets and Consolidated Statements of Income.

Funding for the plans above during calendar year 2026 is expected to be approximately $23.5 million, of which $20.0 million pertains to the QRP. Management monitors plan assets and liabilities and may, at its discretion, increase plan funding levels above the minimum in order to achieve a desired funded status and avoid or minimize potential benefit restrictions.

The accumulated benefit obligation for the QRP and the SERP is presented below:

Benefits expected to be paid for the QRP, SERP, and PBOP over the next 10 years are as follows:

No assurance can be made that actual funding and benefits paid will match these estimates.

For PBOP measurement purposes, the per capita cost of the covered health care benefits medical rate trend assumption is 5.0%, declining to 4.5%. Specific contributions are made for health care benefits of employees who retire after 1988, but Southwest Gas pays all covered health care costs for employees who retired prior to 1989. The medical trend rate assumption noted above applies to the benefit obligations of pre-1989 retirees only.

The service cost component of net periodic benefit costs included in the table below is part of an overhead loading process associated with the cost of labor. The overhead process ultimately results in allocation of that portion of overall net periodic benefit costs to the same accounts to which productive labor is charged. As a result, service costs become components of various accounts, primarily Operations and maintenance expense, Net regulated operations plant, and Deferred charges and other assets for both the Company and Southwest Gas. The non-service cost components of net periodic benefit cost are reflected in Other income (deductions) on the Consolidated Statements of Income of each entity, based on accounting guidance for the presentation of such costs. Variability in total net periodic benefit cost between periods, especially with regard to the QRP, is subject to changes in underlying actuarial assumptions between periods, notably the discount rate.

Components of net periodic benefit cost:

Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income

The table above discloses the net gain or loss and prior service cost recognized in Other comprehensive income, separated into (a) amounts initially recognized in Other comprehensive income, and (b) amounts subsequently recognized as adjustments to Other comprehensive income as those amounts are amortized as components of net periodic benefit cost.

The following table sets forth, by level within the three-level fair value hierarchy, the fair values of the assets of the QRP and the PBOP as of December 31, 2025 and 2024. The SERP has no assets.

(1)Government fixed income consists of government-related securities including cash and cash equivalent securities as well as assets invested in the Treasury futures overlay and associated cash collateral.

(2)The Mutual funds category is a balanced fund that invests in diversified portfolios of common stocks, preferred stocks, and fixed-income securities. Under normal circumstances, the fund invests between 25% and 75% of its total assets in equity securities and at least 25% in fixed-income investments. It may also invest up to 30% in non-U.S. securities. The fund seeks regular income, conservation of principal, and an opportunity for long-term growth of principal and income.

(3)These funds are collective short-term funds that invest in Treasury bills and money market funds and are used as a temporary cash repository.

(4)The commingled trust equity funds include common collective trusts that invest in diversified portfolios of securities regularly traded on securities exchanges. These funds are shown in the above table at NAV, which is the value of securities in the fund less the amount of any liabilities outstanding. Strategies employed by the funds include investment in:

▪Global equities, including domestic (U.S.) and international equities

▪International developed countries equities

▪Domestic (U.S.) equities

▪Emerging markets equities

Shares in the commingled trust equity funds may be redeemed givenone business day advance notice. The global fund provides diversified exposure to global equity markets. The fund seeks to provide long-term capital growth by investing primarily in securities listed on the major developed equity markets of the U.S., Europe, and Asia, as well as within those listed on emerging country equity markets on a tactical basis.

The international fund invests in international financial markets, primarily those of developed economies in Europe and Asia. The fund invests primarily in equity securities issued by foreign corporations but may invest in other securities perceived as offering attractive investment return opportunities.

The domestic equities securities funds include a large and medium capitalization fund and a small capitalization fund. The large and medium capitalization fund is designed to track the performance of the large and medium capitalization companies contained in the index, which represents approximately 90% of the market capitalization of the U.S. stock market. The small capitalization fund is designed to provide maximum long-term appreciation through investments that are well diversified by industry.

The emerging markets fund invests in countries defined as an emerging market country. Fund investments are made directly in each country or, where direct investment is inefficient or prohibited, through appropriate financial instruments or participation in commingled funds. Major emerging markets include Brazil, India, China, and other developing countries around the world.

(5)The commingled trust fixed income funds consist primarily of fixed income debt securities issued by the U.S. Treasury, government agencies, and fixed income debt securities issued by corporations. The fixed income fund investments may include the use of high yield international fixed income securities and other instruments, including derivatives, to ensure prudent diversification over a broad spectrum of investments. The changes in the value of the fixed income funds are intended to offset the changes in the pension plan liabilities due to changes in the discount rate.

(6) The insurance company general account contracts are annuity insurance contracts used to pay the pensions of employees who retired prior to 1989. The balance of the account disclosed in the above table is the contract value, which is the result of deposits, withdrawals, and interest credits.

Note 11 - Income Taxes

The following is a summary of income before taxes from continuing operations:

Income tax expense (benefit) consists of the following:

A reconciliation of the U.S. federal statutory rate to the Southwest Gas Holdings, Inc. consolidated effective income tax rate (and the sources of these differences and the effect of each) are summarized as follows:

(1) State taxes in Arizona made up the majority (greater than 50%) of the tax effect in this category. In addition, this reflects the impact of the revised state apportionment rates recorded in 2025.

Total cash paid for income taxes, net of refunds, are detailed below. Please note that the table below includes totals for both continuing and discontinued operations.

Deferred tax assets and liabilities consist of the following:

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:

At December 31, 2025, the Company has a U.S. federal net operating loss carryforward of $599.4 million on a tax return basis. As of the same date, the Company has $435.7 million of state net operating loss carryforwards on a tax return basis. Depending on the jurisdiction in which the state net operating loss was generated, the carryforwards will begin to expire in 2041.

Certain amounts in this disclosure have been revised as discussed in Note 3 -Revision of Previously Issued Financial Statements.

The following is a summary of income before taxes:

Income tax expense (benefit) consists of the following:

A reconciliation of the U.S. federal statutory rate to the Southwest Gas effective income tax rate (and the sources of these differences and the effect of each) are summarized as follows:

(1) State taxes in Arizona made up the majority (greater than 50%) of the tax effect in this category. In addition, this reflects the impact of the revised state apportionment rates recorded in 2025.

Income taxes paid, net of refunds, are as follows:

Deferred tax assets and liabilities consist of the following:

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:

Southwest Gas Holdings, Inc. and Southwest Gas Corporation:

In assessing whether uncertain tax positions should be recognized in its financial statements, management first determines whether it is more-likely-than-not that a tax position will be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. In evaluations of whether a tax position has met the more-likely-than-not recognition threshold, management presumes that the position will be examined by the appropriate taxing authority that would have full knowledge of all relevant information. For tax positions that meet the more-likely-than-not recognition threshold, management measures the amount of benefit recognized in the financial statements at the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement. Unrecognized tax benefits are recognized in the first financial reporting period in which information becomes available indicating that such benefits will more-likely-than-not be realized. For each reporting period, management applies a consistent methodology to measure unrecognized tax benefits, and all unrecognized tax benefits are reviewed periodically and adjusted as circumstances warrant. Measurement of unrecognized tax benefits is based on management’s assessment of all relevant information, including prior audit experience, the status of audits, conclusions of tax audits, lapsing of applicable statutes of limitation, identification of new issues, and any administrative guidance or developments.

The Company and Southwest Gas recognize interest expense and penalties related to income tax matters in income tax expense. The amount of tax-related interest income for 2023 through 2025 was not significant.

The Company and its subsidiaries file a consolidated federal income tax return in the U.S. and in various states. With few exceptions, the Company is no longer subject to U.S. federal, state and local income tax examinations for years before 2021.

The Company and each of its subsidiaries, including Southwest Gas, participate in a tax sharing agreement to establish the method for allocating tax benefits and losses among members of the consolidated group. The consolidated federal income tax is apportioned among the subsidiaries using a separate return method. According to the terms of the tax sharing agreement, the Company will pay Southwest Gas for the tax attributes that will be utilized in 2025 (primarily used to offset the taxable gain on the sale of Centuri).

In April 2023, the IRS issued Revenue Procedure 2023-15, which provides a safe harbor method of accounting that taxpayers may use to determine whether expenditures to repair, maintain, replace, or improve natural gas transmission and distribution property must be capitalized for tax purposes. Southwest Gas adopted this change in tax accounting method with its 2024 U.S. federal income tax return filing in 2025, and the safe harbor method increased the total tax repair deductions. Southwest Gas Holdings, Inc. and Southwest Gas’ deferred taxes reflect the impacts of this adoption and are not material to the consolidated financial statements overall.

Note 12 - Share-Based Compensation

At December 31, 2025, the following share-based compensation plans existed at the Company: an omnibus incentive plan and a restricted stock/unit plan. The fair value of share grants is primarily based on the closing price of the Company’s stock on the date of grant. All share grants in 2025, including time-lapse restricted stock units and performance stock units, occurred under the omnibus incentive plan. The table below shows total share-based plan compensation expense which was recognized in the Company’s Consolidated Statements of Income:

Omnibus Incentive Plan

The omnibus incentive plan is used to promote the long-term growth and profitability of the Company, including its subsidiaries, by providing directors, employees, and certain other individuals, with incentives to increase stockholder value and otherwise contribute to the success of the Company. In addition, the plan enables the Company to attract, retain, and reward the best available persons for positions of responsibility. The omnibus incentive plan provides for the grant of stock options, stock appreciation rights, restricted stock, restricted stock units, performance stock units, and other equity-based, as well as cash, awards. Employees, directors, and consultants who provide services to the Company or any subsidiary may be eligible under this plan. For grants under the omnibus incentive plan, directors continue to immediately vest in the shares upon grant but are provided the option to defer receipt of equity compensation until they leave the Board.

Performance-based incentive opportunities under the ongoing programs of the omnibus plan were granted to all officers of Southwest Gas in the form of performance stock units and are based, depending on the officer, on consolidated or Southwest Gas earnings per share, utility net income, and utility return on equity, with an adjustment, where relevant, based on total shareholder return compared to peer companies and, for all participants, measured over athree-year forward performance period. Performance stock units are restricted based on vesting, and in this case, further subject to future performance determinations against relevant benchmarks. From time to time, special awards may be granted, as permissible under the omnibus plan, that are recognized based on the relevant conditions of the grant and accounting determinations for recognition and, in 2024, three officers received special performance stock unit awards with accelerated vesting provisions for certain termination events. In 2025, one officer received a special performance stock unit award with accelerated vesting provisions for certain termination events. Southwest Gas recorded $6.2 million, $5.2 million, and $1.1 million of estimated compensation expense associated with the collective performance stock unit awards during 2025, 2024, and 2023, respectively. Performance stock unit awards provide for accelerated vesting in certain limited termination events, with vesting in the ultimate award, if any, generally prorated based on the number of months of employment during thethree-year forward vesting period.

Conversely, with regard to management, grants under the omnibus plan are of time-lapse restricted stock units with graded vesting (and issuance in the form of common stock) occurring (following grant) at the rate of 40% at the end of year one and 30% at the end of years two and three. Accelerated vesting occurs based on retirement eligibility.

Restricted stock/units under the restricted stock/unit plan were previously granted to attract, motivate, retain, and reward key employees of the Company with an incentive to attain high levels of individual performance and improved financial performance. The legacy plan was also established to attract, motivate, and retain experienced and knowledgeable directors. All remaining shares under the legacy restricted stock/unit plan (in regard to employees) were issued during 2021; remaining unissued legacy program shares relate solely to directors, and such shares were immediately vested at the time of grant, with distribution to occur when service on the Board ends.

No new grants are made under the legacy plan as all future stock-based incentive compensation, including with regard to restricted stock, is granted under programs of the omnibus incentive plan, which for directors, with advance election, issuance may occur upon leaving Board service.

The following table summarizes the activity of the omnibus incentive plan and restricted stock/units programs as of December 31, 2025:

(1)Includes shares for retiree payouts and those converted for taxes.

The weighted average grant date fair value of performance stock units and time-lapse restricted stock units granted in 2024 was $68.54 and $62.55, respectively, and in 2023 was $62.78 for performance stock units and $62.83 for time-lapse restricted stock units.

As of December 31, 2025, total compensation cost related to all unvested shares not yet recognized is $7.3 million, which is expected to be recognized over a weighted average period of 1.6 years.

Note 13 - Dispositions

In December 2022, the Company announced that the Board unanimously determined to take strategic actions to simplify the Company’s portfolio of businesses. These actions included entering into a definitive agreement to sell 100% of MountainWest in an all-cash transaction to Williams for $1.5 billion in total enterprise value, subject to certain adjustments, which closed in the first quarter of 2023. Additionally, the Company determined it would pursue a separation of Centuri, including forming a new independent publicly traded utility infrastructure services company.

Centuri

In April 2024, the Company and Centuri announced the completion of the Centuri IPO, prior to which Centuri was a wholly owned subsidiary of the Company. Immediately upon the completion of the Centuri IPO, the Company continued to own approximately 81% of the outstanding shares of common stock of Centuri.

In May 2025, the Company completed a secondary public offering of 10,350,000 shares of Centuri’s common stock owned by the Company (inclusive of 1,350,000 shares related to the exercise of the overallotment option) at a price of $17.50 per share. In addition, the Company sold 2,857,142 shares at a price equal to the public offering price to the Icahn investment entities in a concurrent private placement. The net proceeds to the Company from this public offering and concurrent private placement, after deducting underwriting discounts and commissions of $6.6 million and other fees, were approximately $224.6 million.

In June 2025, the Company completed an additional secondary public offering of 11,212,500 shares of Centuri’s common stock owned by the Company (inclusive of 1,462,500 shares related to the exercise of the overallotment option) at a price of $20.75 per share. The net proceeds to the Company from the public offering, after deducting underwriting discounts and commissions of $8.6 million and other fees, were approximately $224.1 million. In addition, in July 2025 the Company closed the concurrent private placement sale of an additional 1,060,240 shares, at a price equal to the June 2025 Centuri public offering price, with Icahn investment entities. The net proceeds to the Company from this concurrent private placement were approximately $22.0 million. After completion of the June 2025 public offering and July 2025 private placement, the Company owned approximately 52.1% of the then-outstanding Centuri common stock.

On August 11, 2025, the Company completed an additional secondary public offering and concurrent private placement sale with Icahn investment entities for a combined total of 18,823,500 shares of Centuri common stock owned by the Company at a price of $19.50 per share. The net proceeds to the Company, after deducting underwriting discounts and commissions of $11.8 million and other fees, were approximately $355.2 million. The Company used the proceeds for the repayment of outstanding indebtedness, the third quarter dividends to stockholders, and will use the remainder for general corporate purposes (see Note 9 - Debt). After completion of the offering and concurrent private placement, the Company owned approximately 30.9% of the then-outstanding Centuri common stock, and therefore, no longer had a controlling financial interest in Centuri. As a result, the Company met the requirements for the deconsolidation of Centuri. In addition, the sale of Centuri, which comprised the Company’s Utility Infrastructure Services segment, represents a strategic shift that has a significant impact on the Company’s operations and financial results. Therefore, the sale meets the criteria to be reported as discontinued operations in accordance with U.S. GAAP. Accordingly, the historical financial results of Centuri, for all periods presented, are reflected in the Consolidated Financial Statements as discontinued operations. On August 11, 2025, following the deconsolidation of Centuri, the Company remeasured its retained 30.9% ownership interest at fair value. This remeasurement resulted in a gain of $222.9 million, which was included in the total gain recognized upon deconsolidation further described below. Subsequent to this date, the Company elected to continue measuring its retained interest, accounted for under the equity method, at fair value through the date of final disposition on September 5, 2025. Upon final disposition, the Company recognized a loss of $9.7 million. After considering the initial fair value adjustment, the Company recorded a net gain of $213.2 million related to the disposition on its retained interest in Centuri.

On September 5, 2025, the Company completed a final additional secondary public offering of 27,362,210 shares of Centuri common stock owned by the Company at a price of $19.18 per share. After completion of the offering, the Company no longer owns any shares of Centuri common stock and no longer has governance rights afforded to it under the Separation Agreement, including the right to nominate any of Centuri’s directors and any remaining consent rights over certain of Centuri’s corporate actions. The net proceeds to the Company from the public offering, after deducting other fees of approximately $900,000, were approximately $524.0 million.

Centuri did not receive any of the proceeds from the series of public offerings or private placements subsequent to the Centuri IPO. The Company used a portion of the proceeds to pay debts at Southwest Gas Holdings and expects to use the remaining proceeds for general corporate purposes, including support for future capital investments at Southwest Gas, as well as the 2028 expansion of Great Basin, and future dividend payments to stockholders that would otherwise have been funded by Southwest Gas.

The following table presents the net proceeds received by the Company for the sale of Centuri common stock subsequent to the Centuri IPO:

(1)Net proceeds, net of transaction costs

Discontinued Operations

The gain on deconsolidation as of August 11, 2025, adjusted during fourth quarter of 2025, is calculated as follows (in thousands):

(1)Centuri’s quoted stock price is used for fair value measurement, which is classified as level 1 in the fair value hierarchy as of August 11, 2025.

(2) Represents adjustment of deemed capital contribution for the Company’s fourth quarter of 2025 results of operations and the filing of 2024 federal and state income tax returns according to the terms of the Tax Assets Agreement.

(3)Includes $120.2 million gain on interest sold and $222.9 million gain on the investment retained.

The following table summarizes the components of assets and liabilities of discontinued operations on the Company’s Condensed Consolidated Balance Sheets at December 31, 2024:

Summarized results from discontinued operations were as follows:

Following the May 2025 sale of Centuri common stock, the Company was no longer eligible to include Centuri in its consolidated federal and certain state income tax returns (tax deconsolidation) and the Company’s tax-free spin protection plan expired. As such, the Company could no longer assert the ability to complete a tax-free disposition of its investment in Centuri. This event required the Company to recognize a previously unrecorded deferred tax liability related to the outside basis of its investment in Centuri. As a result, the Company recognized tax expense of $52.8 million related to the recognition of outside basis differences. Following the sale of the Company’s shares of Centuri common stock in August 2025, the Company was no longer eligible to include Centuri in its remaining state income tax returns.

In addition, the Company recorded a tax benefit of $24.1 million related to deferred tax assets. These benefits reflect state net operating losses that are now expected to be utilized in connection with the disposition of Centuri shares.

As a result of the Centuri deconsolidation in August 2025, the Company recorded an income tax expense of $82.7 million. Furthermore, the Company recorded an income tax benefit of $5.6 million primarily related to the final disposition of Centuri, valuation allowance release, and for other separation costs. The Company also reflected a $2.0 million income tax benefit from the results of Centuri’s operations through the deconsolidation date resulting in a total income tax expense of $103.7 million.

On February 24, 2025, the Company entered into a Tax Assets Agreement with Centuri. The Tax Assets Agreement addresses the Company’s arrangements with Centuri with respect to certain Tax Assets that each company will retain following any deconsolidation for U.S. federal and relevant state income tax laws. Under the terms of the Tax Assets Agreement, the Company contributed $80.7 million, inclusive of the $24.3 million recording in the fourth quarter of 2025, of Tax Assets to Centuri, which were treated as a deemed capital contribution. This amount is subject to change and will be finalized upon the filing of the 2025 final consolidated or combined federal and state income tax returns. Any future changes to the Tax Assets contributed to Centuri will be recorded in discontinued operations.

The Company had $7.7 million of redeemable noncontrolling interests at December 31, 2024 that was disposed of in connection with the Centuri separation.

Note 14 - Previously Issued Condensed Consolidated Financial Statements (Unaudited)

Southwest Gas Holdings, Inc.– Restatement of Previously Issued Condensed Consolidated Financial Statements

In connection with the preparation of this Form 10-K for the year ended December 31, 2025, management identified errors in the calculation of estimated deferred income tax liabilities associated with state income taxes. The errors arose following the Company’s sale of shares of Centuri’s common stock in the second and third quarters of 2025, which resulted in the tax deconsolidation of Centuri. The errors occurred because the Company did not update estimated future state apportionment rates following the Company’s sale of 13,207,142 shares of Centuri common stock on May 22, 2025, which resulted in income tax deconsolidation for Arizona, and subsequently following the Company's sale of 18,823,500 shares of Centuri common stock on August 11, 2025, which resulted in income tax deconsolidation for the remaining states, primarily California. As a result, income tax expense and net deferred income tax liabilities were understated by approximately $27.3 million as of and for the three and six months ended June 30, 2025, $7.8 million for the three months ended September 30, 2025 and $35.1 million as of and for the nine months ended September 30, 2025. Additionally, we corrected the September 30, 2025, Consolidated Balance Sheet for an error of $75.0 million related to the classification of current maturities of long-term debt which were included in long-term debt rather than short-term.

The Company intends to correct these financial statements through restatements when these periods are presented in a future periodic filing. The impact of the restatements are presented in the tables below for the three and six months ended June 30, 2025 and the three and nine months ended September 30, 2025. There is no impact to annual results as the errors originated and are being corrected within the same annual period.

The following tables summarize the impact of the correction of the errors to our restated unaudited Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Income, Consolidated Statements of Comprehensive Income, Consolidated Statements of Cash Flows and Consolidated Statements of Equity for each interim period for the three and six months ended June 30, 2025 and the three and nine months ended September 30, 2025. The amounts labeled “As Reported” were derived from our Quarterly Reports on Form 10-Q filed on August 6, 2025, and November 5, 2025, respectively.

The effects of the Company’s prior-period errors on our Condensed Consolidated Financial Statements are as follows:

Southwest Gas Corporation – Revision of Previously Issued Financial Statements

As discussed in Note 3 -Revision of Previously Issued Financial Statements, in connection with the preparation of the Company’s 2025 Form 10-K, management identified errors in the calculation of the estimated deferred income tax liabilities associated with state income taxes. The issues result from not timely updating estimated apportionment rates to reflect certain events. For Southwest Gas, the errors date back to the formation of Southwest Gas Holdings in 2017, when Southwest Gas and Centuri became wholly-owned subsidiaries of Southwest Gas Holdings. These errors were determined to be not material to any previously issued Southwest Gas financial statements. As a result of the cumulative magnitude of the error, Southwest Gas revised the historical financial statements. Southwest Gas also revised the historical financial statements to correct other previously identified immaterial errors.

The Company intends to correct these financial statements through revisions when these periods are presented in a future periodic filing. The impacts of the revisions are presented in the tables below:

Note 15 - Commitments and Contingencies

The Company and Southwest Gas are defendants in miscellaneous legal proceedings. They are also parties to various regulatory proceedings. The ultimate dispositions of these proceedings are not presently determinable; however, it is the opinion of management that no litigation or regulatory proceedings to which the Company and Southwest Gas are currently subject will have a material adverse impact on their financial position, results of operations, or cash flows.

The Company maintains excess liability insurance that covers Southwest Gas for various risks associated with the operation of the natural gas pipelines and facilities. In connection with these liability insurance policies, Southwest Gas is responsible for an initial deductible or self-insured retention amount per incident after which the insurance carriers would be responsible for amounts up to the policy limits. For the policy period of August 2025 to July 2026, these liability insurance policies require Southwest Gas, as applicable, to be responsible for the first $1.0 million (self-insured retention) of each incident plus a supplemental retention aggregate of $4.0 million in the policy year. When amounts are expected to be incurred above these amounts, subject to insurance carrier indemnity, a liability is recognized for the additional amount, in addition to a receivable, associated with amounts expected to be indemnified by the insurance carrier amounts, without impact to earnings.

Through an assessment process of commitments and contingencies of any kind, the Company and Southwest Gasmay determine that certain costs are likely to be incurred in the future related to specific legal matters. In these circumstances and in accordance with accounting policies, the Company and Southwest Gas will make an accrual, as necessary.

Note 16 - Segment Information

The Company’s businesses were managed within the Natural Gas Distribution segment (Southwest Gas), the Utility Infrastructure Services segment (Centuri), and the Pipeline and Storage segment (MountainWest) through February 2023. The Company disposed of its Pipeline and Storage segment (MountainWest) in February 2023 and disposed of its Utility Infrastructure Services segment (Centuri) in August 2025 see Note 13 - Dispositions. The Company and Southwest Gas consist of a single reportable segment (Natural Gas Distribution) for all periods presented in these financial statements.

The Utility Infrastructure Services segment is presented as discontinued operations in the Consolidated Statements of Income and, as such, have been excluded from continuing operations and segment results. Previously reported results for the Natural Gas Distribution segment was not impacted by the Centuri deconsolidation or the revisions discussed in Note 3 -Revision of Previously Issued Financial Statements.

The Pipeline and Storage segment (MountainWest) was primarily engaged in the business of providing interstate transportation and underground storage services. The MountainWest sale did not meet the criteria for reporting discontinued operations as the sale did not represent a strategic shift that would have a major effect on the Company’s operations or financial results. Previously reported results for the Pipeline and Storage segment was not impacted by the Centuri deconsolidation or the revisions discussed in Note 3 -Revision of Previously Issued Financial Statements.

The Company’s CEO and Southwest Gas’ CEO and President have been identified as the CODM. The CODM reviews the Company’s income (loss) from continuing operations and Southwest Gas’ net income as reported on their respective consolidated statements of income in assessing performance and allocating resources. The CODM considers budget-to-actual variances against these metrics when making decisions about allocating capital and personnel. The CODM also uses income (loss) from continuing operations and net income to assess the return on assets, margin earned, and in assessing the compensation of certain employees.

Because both the Company and Southwest Gas operate as a single reportable segment, the related disclosure information is presented in the applicable sections. The other significant amounts required for disclosure are included within income (loss) from continuing operations and net income. Revenues from external customers are reported as “Revenues from contracts with customers” in Note 6 - Revenuefor the years ended December 31, 2025, and December 31, 2024, and capital expenditures are reported as “Capital expenditures and property additions” in the consolidated statements of cash flows for the years ended December 31, 2025 and December 31, 2024. The measures of assets for the Company and Southwest Gas are reported as “Total assets” on their respective consolidated balance sheets. Refer to these statements for the results of the Natural Gas Distribution segment for the years ended December 31, 2025, December 31, 2024 and December 31, 2023.

As discussed above, the Utility Infrastructure Services segment was reclassified into discontinued operations and the Company only had multiple segments in calendar year 2023. The financial information pertaining to the Natural Gas Distribution and Pipeline and Storage segments as of and for the year ended December 31, 2023 is presented in the tables below. The accounting policies of the segments are the same as those described in Note 2 - Summary of Significant Accounting Policies. In order to reconcile to net income as disclosed in the Consolidated Statements of Income, an Other column is included below associated with certain expenses that represent the corporate and administrative activities associated with Southwest Gas Holdings, such as Operations and maintenance expenses and net interest deduction.

(1) The information for the year ended December 31, 2023 presented for MountainWest reflects activity from January 1, 2023 through February 13, 2023 (the last full day of its ownership by the Company).

(2) Other segment items for each reportable segment includes:

•Natural Gas Distribution: Depreciation and amortization, Taxes other than income taxes, Net interest deductions, and Other income (deductions).

•Pipeline and Storage: Depreciation and amortization, Taxes other than income taxes, Goodwill impairment and loss on sale, Net interest deductions, and Other income (deductions).

(1) The information for the year ended December 31, 2023 presented for MountainWest reflects activity from January 1, 2023 through February 13, 2023 (the last full day of its ownership by the Company).