ADTRAN Holdings, Inc.

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

GENERAL

ADTRAN Holdings, Inc. (“Adtran” or the “Company”) is a leading global provider of networking and communications platforms, software, systems and services focused on the broadband access market, serving a diverse domestic and international customer base in multiple countries that includes large, medium and small Service Providers, alternative Service Providers, such as utilities, municipalities and fiber overbuilders, cable/MSOs, SMBs and distributed enterprises, including Fortune 500 companies with sophisticated business continuity applications; and federal, state and local government agencies. Our innovative solutions and services enable voice, data, video and internet-communications across a variety of network infrastructures and are currently in use by millions worldwide. We support our customers through our direct global sales organization and distribution networks. Our success depends upon our ability to increase unit volume and market share through the introduction of new products and succeeding generations of products having optimal selling prices and increased functionality as compared to both the prior generation of a product and to the products of competitors in order to gain market share. To service our customers and grow revenue, we are continually conducting research and developing new products addressing customer needs and testing those products for the specific requirements of the particular customers. We offer a broad portfolio of flexible software and hardware network solutions and services that enable Service Providers to meet today’s service demands, while enabling them to transition to the fully converged, scalable, highly-automated, cloud-controlled voice, data, internet and video network of the future. In addition to our global headquarters in Huntsville, Alabama, and our European headquarters in Munich, Germany, we have sales and research and development facilities in strategic global locations.

The Company solely owns ADTRAN, Inc. and is the majority shareholder of Adtran Networks. ADTRAN, Inc. is a leading global provider of open, disaggregated networking and communications solutions. Adtran Networks is a global provider of network solutions for data, storage, voice and video services. We believe that the combined technology portfolio can best address current and future customer needs for high-speed connectivity from the network core to the end consumer, especially upon the convergence of solutions at the network edge.

Domination and Profit and Loss Transfer Agreement, Liquidity, Credit Facility and Notes Offering

The DPLTA between the Company, as the controlling company, and Adtran Networks, as the controlled company, which was executed on December 1, 2022, became effective on January 16, 2023, as a result of its registration with the commercial register (Handelsregister) of the local court (Amtsgericht) at the registered seat of Adtran Networks (Jena).

Under the DPLTA, subject to certain limitations pursuant to applicable law and the specific terms of the DPLTA, (i) the Company is entitled to issue binding instructions to the management board of Adtran Networks, (ii) Adtran Networks will transfer its annual profit to the Company, subject to, among other things, the creation or dissolution of certain reserves, and (iii) the Company will absorb the annual net loss incurred by Adtran Networks. The Company’s payment obligation in satisfaction of the requirement that it absorb Adtran Networks’ annual net loss applied to the net loss generated by Adtran Networks in 2025 and it will apply to any net loss generated by Adtran Networks in 2026.

Pursuant to the terms of the DPLTA, each Adtran Networks shareholder (other than the Company) has received an offer to elect either (1) to remain an Adtran Networks shareholder and receive from us an Annual Recurring Compensation payment, or (2) to receive Exit Compensation plus guaranteed interest. The guaranteed interest under the Exit Compensation is calculated from the effective date of the DPLTA to the date the shares are tendered, less any Annual Recurring Compensation paid. The guaranteed interest rate is 5.0% plus a variable component (according to the German Civil Code) that was 1.27% as of March 31, 2026. Assuming all the minority holders of currently outstanding Adtran Networks shares were to elect the second option, we would be obligated to make aggregate Exit Compensation payments, including guaranteed interest, of approximately €304.4 million or approximately $351.7 million, based on an exchange rate as of March 31, 2026, and reflecting interest accrued through March 31, 2026 during the pendency of the appraisal proceedings discussed below. Shareholders electing the first option of Annual Recurring Compensation may later elect the second option. The opportunity for outside Adtran Networks shareholders to tender Adtran Networks shares in exchange for Exit Compensation had been scheduled to expire on March 16, 2023. However, due to the appraisal proceedings that were initiated in 2023 in accordance with applicable German law, this time period for tendering shares has been extended pursuant to the German Stock Corporation Act (Aktiengesetz) and will end two months after the date on which a final decision in such appraisal proceedings has been published in the Federal Gazette (Bundesanzeiger). Following the court's decision on a procedural matter in the DPLTA appraisal proceedings on July 14, 2025, the trial on the merits of the DPLTA has recommenced. It is expected to take a minimum of 12 months for a ruling of the court on the merits and such ruling will most likely be appealed, which would be expected to take an additional 12-24 months to be resolved. Accordingly, the Company does not expect a final decision on the DPLTA appraisal proceedings to be rendered and published prior to 2027, and most likely not until 2028 or beyond.

Additionally, our obligation to pay Annual Recurring Compensation under the DPLTA is a continuing payment obligation, which will amount to approximately €7.8 million (or $9.0 million based on the current exchange rate) per year assuming none of the minority Adtran Networks shareholders as of March 31, 2026 were to elect Exit Compensation. The foregoing amounts do not reflect any potential increase in payment obligations that we may have depending on the outcome of ongoing appraisal proceedings in Germany. The Annual Recurring Compensation is due on the third banking day following the ordinary general shareholders’ meeting of Adtran Networks for the respective preceding fiscal year (but in any event within eight months following expiration of the fiscal year). With respect to the 2025 fiscal year, Adtran Networks’ ordinary general shareholder meeting is scheduled for the second quarter of 2026, and the Annual Recurring Compensation will be due on the third banking day following the meeting. During the three months ended March 31, 2026 and 2025, we accrued $2.2 million and$2.4 million, respectively, in Annual Recurring Compensation. The Annual Recurring Compensation is reflected as an increase to retained deficit in the Condensed Consolidated Balance Sheets.

On July 18, 2022, ADTRAN, Inc., as the borrower, and ADTRAN Holdings, Inc. entered into a credit agreement with a syndicate of banks, including Wells Fargo Bank, National Association, as administrative agent (“Administrative Agent”), and the other lenders named therein (“Credit Agreement”), which has since been amended six times. The Company had access to $319.2 million on its Credit Facility for future borrowings based on debt covenant compliance metrics. The financial covenants under the Credit Agreement, as amended, require the Company to maintain a Consolidated Total Net Leverage Ratio of 5.00 x, a Consolidated Senior Secured Net Leverage Ratio of 3.25 x (4.0 x to 3.5 x during a Springing Covenant Period) and a Consolidated Fixed Charge Coverage Ratio of 1.25 x (as such terms are defined in the Credit Agreement). In addition, during a Springing Covenant Period the cash and cash equivalents of the credit parties must be at least $50.0 million and the cash and cash equivalents of the Company and its subsidiaries must be at least$70.0 million. The Credit Agreement matures in July 2027. The Company intends to refinance or replace the existing Credit Agreement with a new credit facility during the second quarter of 2026. There can be no assurances that this renewal will occur on terms acceptable to the Company, or at all.

On October 18, 2022, the Company's Board of Directors authorized the Company to purchase additional shares of Adtran Networks through open market purchases not to exceed 15,346,544 shares.

As of March 31, 2026, and as of the date of issuance of these financial statements, the Company has sufficient liquidity to meet the majority of its payment obligations under the DPLTA pertaining to Exit Compensation. For the three months ended March 31, 2026, approximately 0.2 million shares of Adtran Networks stock were tendered to the Company and Exit Compensation of €3.6 million or approximately $4.1 million are to be settled in cash in April 2026. For the three months ended March 31, 2025, less thanone thousand shares of Adtran Networks stock were tendered to the Company and exit compensation payments of €12 thousandor $13 thousand based on the applicable exchange rates at the time of the transaction were paid to Adtran Networks shareholders. We believe the probability that more than a small minority of Adtran Networks shareholders elect to receive Exit Compensation in the next twelve months is remote based on the following factors: (i) the shareholders can exercise their right to receive the Exit Compensation until two months after publication of the final decision in the appraisal proceedings and we do not expect the final decision to be published within the next 12 months; (ii) the diverse base of shareholders that must make this election on an individual shareholder basis; (iii) the fact the date of a decision by the court on the merits of the case is uncertain, it will most likely take a minimum of 12 months for a ruling and, thereafter, an expected appeal process will take a further 12-24 months to resolve; (iv) the current guaranteed Annual Recurring Compensation payment; and (v) the current trading value of Adtran Networks shares.

Moreover, on September 19, 2025, the Company issued $201.3 million aggregate principal amount of convertible senior notes due 2030 (the “Notes”). The Notes accrue interest at a rate of 3.75% per annum, payable semi-annually in arrears on March 15 and September 15 of each year, beginning March 15, 2026. Unless repurchased earlier, redeemed, or converted, the Notes will mature on September 15, 2030. After deducting the initial purchasers’ discounts, commissions, and estimated offering expenses, the Company received net proceeds of $192.6 million.

The Company believes that its cash and cash equivalents, working capital management initiatives and availability to access cash under the Wells Fargo credit facility or other future sources of capital will be adequate to meet our business operating requirements, our capital expenditures and our expected obligations under both the Notes and the DPLTA, including anticipated levels of Exit Compensation, as well as to support our ability to continue to comply with our debt covenants under the Credit Facility for at least the next twelve months, from the issuance of these financial statements. See Note 10, Credit Agreements, for additional information regarding the terms of the Amendments of the Wells Fargo Credit Agreement.

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The accompanying unaudited Condensed Consolidated Financial Statements of ADTRAN Holdings, Inc. and its subsidiaries have been prepared pursuant to the rules and regulations of the SEC applicable to interim financial information presented in Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles in the United States of America (“U.S. GAAP”) for complete financial statements are not included herein. The December 31, 2025, Condensed Consolidated Balance Sheet is derived from audited financial statements but does not include all disclosures required by U.S. GAAP for annual financial statements.

In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in ADTRAN Holdings, Inc. Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on February 26, 2026.

Use of Estimates

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, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Significant estimates include allowance for credit losses on accounts receivable and contract assets, excess and obsolete inventory reserves, determination and accrual of the deferred revenue related to performance obligations under contracts with customers, estimated costs to complete obligations associated with deferred and accrued revenue and network installations, estimated income tax provision and income tax contingencies, fair value of stock-based compensation, assessment of goodwill and other intangibles for impairment, estimated lives of intangible assets, estimates of intangible assets upon measurement, estimated pension liability and fair value of investments and estimated contingent liabilities. Actual amounts could differ significantly from these estimates.

We assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to us and the unknown future impacts of ongoing inflationary pressures, continued elevated interest rates, instability in the financial services industry, currency fluctuations and political tensions as of March 31, 2026, and through the date of this report. These conditions could result in further impacts to the Company's consolidated financial statements in future reporting periods. The accounting matters assessed included, but were not limited to, the allowance for credit losses, stock-based compensation, carrying value of goodwill, intangibles and other long-lived assets, financial assets, valuation allowances for tax assets, revenue recognition and costs of revenue.

During the three months ended March 31, 2026, there were no other significant changes to our critical accounting policies or estimates from those described in the financial statements contained in the 2025 Form 10-K.

Recent Accounting Pronouncements Not Yet Adopted

In September 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") 2025-06, "Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software," which is intended to modernize the accounting for the costs of internal-use software given the evolution of software development to the incremental and iterative development method. The amendments remove all references to prescriptive and sequential development stages and, instead, require an entity to start capitalizing software costs when management has authorized and committed to funding the software project, and it is probable that the project will be completed and the software will be used to perform the function intended. The amendments are effective for annual reporting periods beginning after December 15, 2027, and interim reporting periods within those annual reporting periods. Early adoption is permitted as of the beginning of an annual reporting period with the amendments to be applied using a prospective, modified or retrospective transition approach. The Company is currently evaluating the impact of adopting this guidance on the consolidated financial statements.

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, as amended by ASU 2025-01, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Clarifying the Effective Date", which applies to all public business entities (PBEs) and is intended to enhance disclosures about specific types of expenses included in the expense captions presented on the face of the income statement as well as disclosures about selling expenses. The amendments are effective prospectively for annual periods beginning after December 15, 2026, and interim reporting periods within annual reporting periods beginning after December 15, 2027. Early adoption and retrospective application are permitted. The Company is currently evaluating the effect that adoption of ASU 2024-03 will have on our disclosures.

Recently Adopted Accounting Pronouncements

There are currently no recently adopted accounting pronouncements that are expected to have a material effect on the Condensed Consolidated Financial Statements.

2. REVENUE AND RECEIVABLES

The following is a description of the principal activities from which revenue is generated by reportable segment:

Network Solutions Segment -Includes hardware and software products that enable a digital future which support the Company's Subscriber, Access & Aggregation, and Optical Networking Solutions.

Services & Support Segment -Includes network design, implementation, maintenance and cloud-hosted services supporting the Company's Subscriber, Access & Aggregation, and Optical Networking Solutions.

Revenue by Category

In addition to the Company's reportable segments, revenue is also reported for the following three categories – Subscriber Solutions, Access & Aggregation Solutions and Optical Networking Solutions.

Our Subscriber Solutions portfolio is used by Service Providers to terminate their access services infrastructure at the customer premises while providing an immersive and interactive experience for residential, business and wholesale subscribers. This revenue category includes hardware- and software-based products and services. These solutions include fiber termination solutions for residential, business and wholesale subscribers, Wi-Fi access solutions for residential and business subscribers, Ethernet switching and network edge virtualization solutions for business subscribers, and cloud software solutions covering a mix of subscriber types.

Our Access & Aggregation Solutions are solutions that are used by communications Service Providers to connect residential subscribers, business subscribers and mobile radio networks to the Service Providers’ metro network, primarily through fiber-based connectivity. This revenue category includes hardware- and software-based products and services. Our solutions within this category are a mix of fiber access and aggregation platforms, precision network synchronization and timing solutions, and access orchestration solutions that ensure highly reliable and efficient network performance.

Our Optical Networking Solutions are used by communications Service Providers, internet content providers and large-scale enterprises to securely interconnect metro and regional networks over fiber. This revenue category includes hardware- and software-based products and services. Our solutions within this category include open optical terminals, open line systems, optical subsystems and modules, network infrastructure assurance systems, and automation platforms that are used to build high-scale, secure and assured optical networks.

The following tables disaggregate revenue by reportable segment and revenue category:

The aggregate amount of transaction price allocated to remaining performance obligations ("RPO") that have not been satisfied as of March 31, 2026 related to non-cancellable contractual maintenance agreements, non-cancellable contractual SaaS and subscription services, and non-cancellable hardware contracts amounted to $159.2 million. The majority of the Company's performance obligations will generally be satisfied within a year and any remaining performance obligations are typically recognized overone tothree years.

The following table provides information about accounts receivable, contract assets and unearned revenue from contracts with customers:

(1)Included in other receivables on the Condensed Consolidated Balance Sheets.

Accounts Receivable

The allowance for credit losses was $1.7 million and $1.3 million as of March 31, 2026, and December 31, 2025, respectively, related to accounts receivable.

Receivables Purchase Agreements

On July 1, 2024, the Company entered into a receivables purchase agreement (the “Factoring Agreement”) with a third-party financial institution (the “Factor”), which accelerates receivable collection and helps to better manage cash flow. Total accounts receivables factored as of the end of March 31, 2026, totaled $26.1 million of which $3.9 million was retained pursuant to the Factoring Agreement in the reserve account. Total accounts receivables factored as of the end of March 31, 2025, totaled $11.2 million of which $3.7 million was retained pursuant to the Factoring Agreement in the reserve account. The Factoring Agreement provides for up to $40.0 million in factoring capacity, subject to eligible receivables and reserve requirements, secured by the receivables.

During the three months ended March 31, 2026 and 2025, the Company received $51.8 million and $31.8 million, in cash proceeds from the Factoring Agreement, respectively. The cost of the Factoring Agreement is included in interest expense in the Condensed Consolidated Statements of Loss and totaled $0.5 million and $0.3 million for the three months ended March 31, 2026 and 2025, respectively.

Contract Assets

No allowance for credit losses was recorded for thethree months ended March 31, 2026 and 2025, respectively, related to contract assets.

Unearned Revenue

Of the outstanding unearned revenue balances as of December 31, 2025, $23.1 million were recognized as revenue during the three months ended March 31, 2026. Of the $52.7 outstanding unearned revenue balances as of December 31, 2024, $21.9 million were recognized as revenue during the three months ended March 31, 2025.

3. INCOME TAXES

The Company’s effective tax rate changed from a benefit of 4.2%of pre-tax loss for the three months ended March 31, 2025, to an expenseof 67.3% of pre-tax income for thethree months ended March 31, 2026. The change in the effective tax rate for the three months ended March 31, 2026, was driven primarily by loss jurisdictions for which the recognition of tax benefits on pre-tax losses incurred during the first quarter of 2026 were limited due to valuation allowance.

The Company continually reviews the adequacy of its valuation allowance and recognizes the benefits of deferred tax assets only as the assessment indicates that it is more likely than not that the deferred tax assets will be recognized in accordance with ASC 740, Income Taxes. As of March 31, 2026, the Company had net deferred tax assets totaling $113.9 million, and a valuation allowance totaling $124.5 million against those deferred tax assets. Our assessment of the realizability of our deferred tax assets includes the evaluation of historical operating results, as well as the evaluation of evidence which requires significant judgment, including the evaluation of our three-year cumulative income position, future taxable income projections and tax planning strategies. Should management’s conclusion change in the future and an additional valuation allowance, or a partial or full release of the valuation allowance becomes necessary, it may have a material effect on our consolidated financial statements.

4. STOCK-BASED COMPENSATION

2024 Stock Incentive Plans

At the annual meeting of stockholders held on May 8, 2024, the Company’s stockholders approved, upon recommendation of the Board of Directors, the adoption of the ADTRAN Holdings, Inc. 2024 Employee Stock Incentive Plan (“2024 Employee Plan”) and the ADTRAN Holdings, Inc. 2024 Directors Stock Plan (“2024 Directors Plan”). Outstanding awards granted under the Company's prior equity incentive plans will remain subject to the terms of such applicable plans, and shares under such plans that are cancelled or forfeited will be available for issuance under the 2024 Employee Plan or the 2024 Directors Plan, as applicable.

As of March 31, 2026,5.5 million shares were available for issuance pursuant to awards that may be made in the future under stockholder-approved equity plans.

For the three months ended March 31, 2026 and 2025, stock-based compensation expense was$1.8 million and $3.2 million, respectively.

PSUs, RSUs and Restricted Stock

The following table summarizes the PSUs, RSUs and restricted stock outstanding as of December 31, 2025, and March 31, 2026 and the changes that occurred during the three months ended March 31, 2026:

The fair value of PSUs with performance conditions, RSUs and restricted stock is equal to the closing price of the Company's stock on the date of grant. The fair value of PSUs with market conditions is calculated using a Monte Carlo simulation valuation method.

As of March 31, 2026, total unrecognized compensation expense related to non-vested portion of performance-based PSUs, market-based PSUs, RSUs and restricted stock was approximately $12.1 million, which will be recognized over the remaining weighted-average period of 2.2 years. Unrecognized compensation expense will be adjusted for actual forfeitures.

5. INVESTMENTS

The Company has cash equivalents and investments which are held at fair value as follows:

(1) The money market fund balances of $0.2 million as of March 31, 2026 and December 31, 2025, are included in cash and cash equivalents on the balance sheet.

Market prices are obtained from a variety of industry standard data providers, large financial institutions and other third-party sources. These multiple market prices are used as inputs into a distribution-curve-based algorithm to determine the daily market value of each security.

U.S. GAAP establishes a three-level valuation hierarchy based upon observable and unobservable inputs for fair value measurement of financial instruments:

• Level 1 – Observable outputs; values based on unadjusted quoted prices for identical assets or liabilities in an active market;

• Level 2 – Significant inputs that are observable; values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly and

• Level 3 – Significant unobservable inputs; values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs could include information supplied by investees.

6. INVENTORY

As of March 31, 2026 and December 31, 2025, inventory, net was comprised of the following:

Inventory reserves are established for estimated excess and obsolete inventory equal to the difference between the cost of the inventory and the estimated net realizable value of the inventory based on estimated reserve percentages, which considers historical usage, known trends, inventory age and market conditions.

7. PROPERTY, PLANT AND EQUIPMENT

Property, plant and equipment consisted of the following:

Long-lived assets used in operations are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable and the undiscounted cash flows estimated to be generated by the asset are less than the asset’s carrying value.

Depreciation expense was $8.1 million and $6.9 million for thethree months ended March 31, 2026 and 2025, respectively, which is recorded in cost of revenue, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of Loss.

Assets Held For Sale

On December 31, 2025, the Company determined that it continued to meet the held for sale criteria pursuant to ASC 360,"Impairment and Disposal of Long-Live Assets" on a portion of the Company's property located at its Huntsville, Alabama campus and ceased recording depreciation on the assets. The Company continues to assess the probability that the sale of its headquarters in Huntsville will occur and has determined it is probable of occurring in the next twelve months.

The Company records assets held for sale at the lower of their carrying value or fair value. The total carrying value of assets held for sale was $11.9 million as of March 31, 2026 and December 31, 2025, respectively, and is separately recorded on the balance sheet.

8. GOODWILL

The changes in the carrying amount of goodwill for the three months ended March 31, 2026 and the twelve months ended December 31, 2025, are as follows:

Goodwill represents the excess purchase price over the fair value of net assets acquired. The Company performs its annual goodwill impairment test as of the first day of the fourth quarter. In addition, the Company performs an interim impairment assessment prior to our annual measurement date whenever events or changes in circumstances indicate that the carrying amount of such assets (or group of assets) may not be recoverable.

No impairment of goodwill was recognized during the three months ended March 31, 2026 and 2025. As of March 31, 2026, accumulated goodwill impairment losses totaled $335.3 million.

9. INTANGIBLE ASSETS

Intangible assets as of March 31, 2026 and December 31, 2025, consisted of the following:

No impairment losses of intangible assets were recorded during the three months ended March 31, 2026 and 2025.

Amortization expense was $16.9 million and $14.9 million in thethree months ended March 31, 2026 and 2025, respectively, and was included in cost of revenue, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of Loss.

During the three months ended March 31, 2026, the Company had development costs of $8.4 million for developed technology assets with a weighted average amortization period ofthree years withno expected residual value.

Estimated future amortization expense of intangible assets is as follows:

10. CREDIT AGREEMENTS

The carrying amounts of the Company's non-current revolving credit facility in its Condensed Consolidated Balance Sheets were as follows:

As of March 31, 2026 and December 31, 2025, the estimated fair value of our revolving credit agreement approximates the carrying value. As of March 31, 2026, the weighted average interest rate on our revolving credit agreement was 8.92%.

Revolving Credit Agreement

On July 18, 2022, ADTRAN, Inc., as the borrower ("U.S. Borrower"), and the Company entered into a credit agreement with a syndicate of banks, including Wells Fargo Bank, National Association, as administrative agent (“Administrative Agent”), and the other lenders named therein (the “Original Credit Agreement”), as amended by the First Amendment to Credit Agreement, dated August 9, 2023 (“Amendment No. 1”), the Second Amendment to Credit Agreement, dated January 16, 2024 (“Amendment No. 2”), the Third Amendment to Credit Agreement, dated March 12, 2024 (“Amendment No. 3”), the Fourth Amendment to Credit Amendment, dated June 4, 2024 among Adtran Networks (the "German Borrower") and the parties set forth above ("Amendment No. 4"), the Fifth Amendment to Credit Agreement and Waiver, dated May 6, 2025, among the German Borrower and the parties set forth above (“Amendment No. 5”), and the Sixth Amendment and Consent Credit Agreement, dated September 16, 2025, among the U.S. Borrower, the German Borrower and the lenders party thereto ("Amendment No. 6"); (the Original Credit Agreement as amended by Amendment No. 1, Amendment No. 2. Amendment No. 3, Amendment No. 4 and Amendment No. 5, the “Existing Credit Agreement”).

As of March 31, 2026, the Amended Credit Agreement provided for a secured revolving credit facility of up to $350.0 million of borrowings, $50.0 million of which is solely available to the German Borrower.

As of March 31, 2026, the Company’s borrowings under the revolving line of credit were$25.0 million. The credit facilities provided under the Amended Credit Agreement mature in July 2027, but the U.S. Borrower may request extensions subject to customary conditions. In addition, the U.S. Borrower may utilize up to $50.0 million of the $350.0 million total revolving facility for the issuance of letters of credit. As of March 31, 2026, the U.S. Borrower had a total of $5.8 million in letters of credit under the Amended Credit Agreement, leaving a net amount (after giving effect to the $25.0 million of outstanding borrowings described above) of $319.2 million available for future borrowings, based on debt covenant compliance metrics. Any future credit extensions under the Amended Credit Agreement are subject to customary conditions precedent. The proceeds of any loans may be used as described above, as well as for working capital and other general corporate purposes.

Moreover, the Amended Credit Agreement provides for a sublimit under the existing $350.0 million revolving commitments in an aggregate amount of $50.0 million (“Subline”), which Subline is available for borrowings by the German Borrower. The Company had no borrowings under the Subline as of March 31, 2026. The existing swing line sublimit and letter of credit sublimit under the Amended Credit Agreement remain available to the U.S. Borrower (and not to the German Borrower). Otherwise, the loans under the Subline are subject to substantially the same terms and conditions under the Amended Credit Agreement (including with respect to the interest rate and maturity date) as the other existing revolving commitments.

11. CONVERTIBLE SENIOR NOTES AND CAPPED CALLS

The outstanding principal and carrying value of the convertible senior notes were as follows:

The estimated fair value of the 2030 Notes was $273.9 million and $217.5 million as of March 31, 2026 and December 31, 2025, respectively. The estimated fair value of the 2030 Notes, based on Level 2 inputs of the valuation hierarchy, were determined based on the quoted bid prices of the 2030 Notes in an over-the-counter market on the last trading day of the reporting period.

The effective interest rate of the 2030 Notes over their expected life is 4.7%. The following is a summary of interest expense for the 2030 Notes:

On September 19, 2025, the Company issued $201.3 million principal amount of its 3.75% convertible senior notes due September 15, 2030. The 2030 Notes were issued pursuant to, and are governed by, an indenture (the “Indenture”), dated as of September 19, 2025, between the Company and U.S. Bank Trust Company, National Association, as trustee (the “Trustee”). The 2030 Notes are the Company’s senior, unsecured obligations and bear interest at a rate of 3.75% per year payable semi-annually in arrears on March 15 and September 15 of each year, beginning on March 15, 2026. Each $1,000 principal amount of the 2030 Notes will be convertible into 86.8206 shares of the Company’s common stock, which is equivalent to a conversion price of approximately $11.52 per share, subject to adjustment upon the occurrence of specified events. In addition, if certain corporate events that constitute a “make-whole fundamental change” (as defined in the Indenture) occur, then the conversion rate will, in certain circumstances, be increased for a specified period of time.

The 2030 Notes are convertible at the option of the holders of the 2030 Notes before June 15, 2030, only under the following circumstances: (1) during any calendar quarter (and only during such calendar quarter) commencing after the calendar quarter ending on December 31, 2025, if the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price for each of at least 20 trading days, whether or not consecu tive, during the last 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (2) during thefive consecutive business days immediately after any 10 consecutive trading day period (such 10 consecutive trading day period, the “measurement period”) if the trading price per $1,000 principal amount of the 2030 Notes for each trading day of the measurement period was less than 98%of the product of the last reported sale price per share of our common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company’s common stock; or (4) if the Company calls (or is deemed to have called) the 2030 Notes for redemption. From and after June 15, 2030, noteholders may convert their 2030 Notes at any time at their election until theclose of business on the second scheduled trading day immediately before the maturity date. The Company will settle conversions by paying cash up to the aggregate principal amount of the 2030 Notes to be converted and paying or delivering, as applicable, cash, shares of its common stock or a combination of cash and shares of its common stock, at the Company’s election, in respect of the remainder, if any, of its conversion obligation in excess of the aggregate principal amount of the Notes being converted, based on the applicable conversion rate.

The 2030 Notes will be redeemable, in whole or in part (subject to certain limitations described below), at the Company’s option at any time, and from time to time, on or after September 20, 2028 and on or before the 46th scheduled trading day immediately before the maturity date, but only if (i) the Notes are “Freely Tradable” (as defined in the Indenture) as of the date the Company sends the related redemption notice, and all accrued and unpaid additional interest, if any, has been paid in full as of the most recent interest payment date occurring on or before the date the Company sends the related redemption notice; and (ii) the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price on (1) each of at least 20 trading days, whether or not consecutive, during the last 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends the related redemption notice; and (2) the trading day immediately before the date the Company sends such redemption notice. However, the Company may not redeem less than all of the outstanding Notes unless at least $70.0 million aggregate principal amount of Notes are outstanding and not called for redemption as of the time the Company sends, and after giving effect to, the related redemption notice. The redemption price will be a cash amount equal to the principal amount of the Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date. In addition, calling (or the deemed calling of) any Note for redemption will constitute a “make-whole fundamental change” with respect to that Note, in which case the conversion rate applicable to the conversion of that Note will be increased in certain circumstances if it is converted during the related redemption conversion period. No sinking fund is provided for the 2030 Notes, which means the Company is not required to redeem or retire the 2030 Notes periodically.

If certain corporate events that constitute a “fundamental change” (as defined in the Indenture) occur, then, subject to a limited exception for certain cash mergers, noteholders may require the Company to repurchase their Notes at a cash repurchase price equal to the principal amount of the Notes to be repurchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change repurchase date. The definition of “fundamental change” includes certain business combination transactions involving the Company and certain de-listing events with respect to the Company’s common stock.

Capped Calls

In connection with the pricing of the 2030 Notes and the exercise of the initial purchasers’ option to purchase additional 2030 Notes, the Company entered into privately negotiated capped call transactions with one of the initial purchasers of the 2030 Notes or its affiliate and certain other financial institutions pursuant to capped call confirmations (collectively, the “Capped Calls”). The premiums paid for the purchases of the Capped Calls were approximately $17.6 million. The Capped Calls have an initial strike price of approximately $11.52 per share, subject to certain adjustments substantially similar to those applicable to the corresponding 2030 Notes. The Capped Calls have an initial cap price of approximately $15.51 per share, subject to certain adjustments. The Capped Calls cover, subject to anti-dilution adjustments, approximately 17.5 million shares of the Company’s common stock.

The Capped Calls are generally expected to reduce potential dilution to the Company’s common stock and/or offset any cash payments that the Company is required to make in excess of the principal amount of any converted 2030 Notes, with such reduction and/or offset subject to a cap, based on the cap price of the Capped Calls.

The Capped Calls are separate transactions and are not part of the terms of the 2030 Notes. The Capped Calls do not meet the criteria for separate accounting as a derivative as they are indexed to the Company's stock and meet the requirements to be classified in equity and, as such, are not remeasured each reporting period.

12. EMPLOYEE BENEFIT PLANS

Pension Benefit Plan

We maintain a defined benefit pension plan covering employees in certain foreign countries. The net amounts recognized in the Condensed Consolidated Balance Sheets for the unfunded pension liability as of March 31, 2026 and December 31, 2025 were as follows:

The Company's defined benefit pension liability represents the projected benefit obligation, which is the actuarial present value of the vested benefits to which the employee is currently entitled based on the employee's expected date of retirement.

The following table summarizes the components of net periodic pension cost related to the Company's defined benefit pension plans:

The components of net periodic pension cost, other than the service cost component, are included in other income, net in the Condensed Consolidated Statements of Loss. Service cost is included in cost of revenue, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of Loss. The Company made contributions to the defined benefit pension plans totaling$1.1 million during the three months ended March 31, 2026 and 2025. Contributions to the defined benefit pension plans for the remainder of 2026 will be limited to benefit payments to retirees which are paid out of the operating cash flows of the Company and are expected to be approximately $1.6 million.

13. EQUITY

Accumulated Other Comprehensive Income

The following tables present the changes in accumulated other comprehensive income, net of tax, by component:

The following tables present the details of reclassifications out of accumulated other comprehensive (loss) income:

The following table presents the tax effects related to the change in each component of other comprehensive (loss) income:

14. REDEEMABLE NON-CONTROLLING INTEREST

As of March 31, 2026 and December 31, 2025, the non-controlling Adtran Networks stockholders’ equity ownership percentage in Adtran Networks was approximately 28.8%and 29.2%, respectively.

The following table summarizes the redeemable non-controlling interest activity for thethree months ended March 31, 2026 and for the year ended December 31, 2025:

Annual recurring compensation payable on untendered outstanding shares under the DPLTA must be recognized as it is accrued. For the three months ended March 31, 2026, we accrued$2.2 million and for the year ended December 31, 2025, the Company accrued $9.3 million, representing the portion of the annual recurring cash compensation to the non-controlling shareholders during such periods. The 2025 Annual Recurring Compensation accrual will be paid after the ordinary general shareholders' meeting of Adtran Networks in 2026. The 2026 Annual Recurring Compensation accrual will be paid after the ordinary general shareholders' meeting of Adtran Networks in 2027.

15. LOSS PER SHARE

The calculation of basic and diluted loss per share for the quarters ended March 31, 2026 and 2025 are as follows:

The following potentially dilutive shares were excluded from the calculation of the diluted weighted average number of shares outstanding as the effect would have been anti-dilutive:

16. SEGMENT INFORMATION

The chief operating decision maker is the Company's Chief Executive Officer who regularly reviews the Company’s financial performance based ontwo reportable segments: (1) Network Solutions and (2) Services & Support.

The Network Solutions segment includes hardware and software products that enable a digital future which support the Company's Subscriber, Access & Aggregation, and Optical Networking Solutions. The Company's cloud-managed Wi-Fi gateways, virtualization software, and switches provide a mix of wired and wireless connectivity at the customer premises. In addition, its Carrier Ethernet products support a variety of applications at the network edge ranging from mobile backhaul to connecting enterprise customers (“Subscriber Solutions"). The Company's portfolio includes products for multi-gigabit service delivery over fiber or alternative media to homes and businesses.

The Services & Support segment offers a comprehensive portfolio of network design, implementation, maintenance and cloud-hosted services supporting its Subscriber, Access & Aggregation, and Optical Networking Solutions. These services assist operators in the deployment of multi-vendor networks while reducing their cost to maintain these networks. The cloud-hosted services include a suite of SaaS applications under the Company's Mosaic One platform that manages end-to-end network and service optimization for both fiber access infrastructure and mesh Wi-Fi connectivity. The Company backs these services with a global support organization that offers on-site and off-site support services with varying SLAs.

The performance of these segments is evaluated based on revenue, gross profit and gross margin; therefore, selling, general and administrative expenses, research and development expenses, interest and dividend income, interest expense, net investment loss, other income, net and income tax (expense) benefit are reported on a consolidated basis only. There is no inter-segment revenue. Asset information by reportable segment is not produced and, therefore, is not reported.

The following tables present information about the revenue and gross profit of the Company's reportable segments:

For the three months ended March 31, 2026 and 2025, $1.7 million and $1.3 million, respectively, of depreciation expense was included in gross profit for our Network Solutions segment. For thethree months ended March 31, 2026 and 2025, less than $0.1 million of depreciation expense was included in gross profit for our Services & Support segment.

Revenue by Geographic Area

The following table presents revenue information by geographic area:

17. COMMITMENTS AND CONTINGENCIES

Legal Matters

From time to time, the Company is subject to or otherwise involved in various lawsuits, claims, investigations and legal proceedings that arise out of or are incidental to the conduct of our business (collectively, “Legal Matters”), including those relating to employment matters, patent rights, regulatory compliance matters, stockholder claims, and contractual and other commercial disputes. Such Legal Matters, even if not meritorious, could result in the expenditure of significant financial and managerial resources. Additionally, an unfavorable outcome in a legal matter, including in a patent dispute, could require the Company to pay damages, entitle claimants to other relief, such as royalties, or could prevent the Company from selling some of its products in certain jurisdictions. The Company records an accrual for any Legal Matters that arise whenever it considers that it is probable that it is exposed to a loss contingency and the amount of the loss contingency can be reasonably estimated. Although the ultimate disposition of asserted claims cannot be predicted with certainty, it is our belief that the outcome of any such claims, either individually or on a combined basis, will not have a material adverse effect on our consolidated financial position.

As disclosed in Amendment No. 1 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, filed with the SEC on May 20, 2025, we identified errors in our previously issued financial statements related to the historical accounting for certain inventory and cost of goods sold transactions (“Adjustment”). The affected periods included the annual periods ended December 31, 2023 and 2024 and the interim periods ended March 31, 2024, June 30, 2024 and September 30, 2024. In connection with the identification of the Adjustment, the Audit Committee oversaw an internal investigation into the circumstances surrounding the Adjustment and its impact on the Company’s historical financial statements. Based on the findings of the internal investigation, it was determined that the underlying errors giving rise to the Adjustment were not properly addressed in the Company’s previously filed financial statements as of and for the years ended December 31, 2024 and 2023 and were not communicated to the Audit Committee or the independent auditors prior to the filing of the initial Annual Report on Form 10-K for the year ended December 31, 2024. The Company has taken certain remedial actions to address the material weaknesses in its internal controls associated with these findings. On August 4, 2025, the Company received a letter from the Atlanta regional office of the SEC in connection with a non-public, fact-finding inquiry, requesting that we voluntarily provide information regarding the internal investigation. The Company is cooperating in response to the SEC’s inquiry and cannot predict the timing or outcome of the inquiry.

DPLTA Appraisal Proceedings

In addition to such Legal Matters, the Company is a party to appraisal proceedings relating to the DPLTA which were originally filed with the Landgericht Meiningen (Meiningen District Court) on February 3, 2023. The DPLTA provides that Adtran Networks shareholders (other than the Company) be offered, at their election, (i) to put their Adtran Networks shares to the Company in exchange for compensation in cash of €17.21 per share, plus guaranteed interest or (ii) to remain Adtran Networks shareholders and receive recurring cash compensation of €0.52 per share for each full fiscal year of Adtran Networks. The appraisal proceedings, which were initiated by certain minority shareholders of Adtran Networks, challenge the adequacy of both forms of compensation. While the Company believes that the compensation offered in connection with the DPLTA is fair, it notes that German courts often adjudicate increases of the cash compensation to plaintiffs in varying amounts in connection with German appraisal proceedings. Therefore, the Company cannot rule out that the first instance court or an appellate court may increase the cash compensation owed to the minority Adtran Networks shareholders. Given the stage of the appraisal proceedings, the Company is currently unable to predict the likely outcome or estimate the potential financial impact, if any, of the appraisal proceedings. If a ruling were to occur and be upheld upon appeal that required the Company to pay significant additional cash compensation to the Adtran Networks minority shareholders, there exists the possibility of a material adverse effect on our financial position and results of operations for the period in which the ruling occurs or future periods.

DPLTA Exit and Recurring Compensation Costs and the Absorption of Adtran Network's Annual Net Loss

Pursuant to the terms of the DPLTA, each Adtran Networks shareholder (other than the Company) has received an offer to elect either (1) to remain an Adtran Networks shareholder and receive from us an Annual Recurring Compensation payment, or (2) to receive Exit Compensation plus guaranteed interest. The guaranteed interest under the Exit Compensation is calculated from the effective date of the DPLTA to the date the shares are tendered, less any Annual Recurring Compensation paid. The guaranteed interest rate is 5.0% plus a variable component (according to the German Civil Code) that was 1.27%as of March 31, 2026. Assuming all the minority holders of currently outstanding Adtran Networks shares were to elect the second option, the Company would be obligated to make aggregate Exit Compensation payments, including guaranteed interest, of approximately €304.4 million or approximately $351.7 million, based on an exchange rate as of March 31, 2026, and reflecting interest accrued through March 31, 2026, during the pendency of the appraisal proceedings discussed below. Shareholders electing the first option of Annual Recurring Compensation may later elect the second option. The opportunity for outside Adtran Networks shareholders to tender Adtran Networks shares in exchange for Exit Compensation had been scheduled to expire on March 16, 2023. However, due to the appraisal proceedings that were initiated in 2023 in accordance with applicable German law, this time period for tendering shares has been extended pursuant to the German Stock Corporation Act (Aktiengesetz) and will end two months after the date on which a final decision in such appraisal proceedings has been published in the Federal Gazette (Bundesanzeiger). Following the court's decision on a procedural matter in the DPLTA appraisal proceedings on July 14, 2025, the proceeding for the trial on the merits of the DPLTA has recommenced. It is expected to take a minimum of 12 months for a ruling of the court on the merits and such ruling will most likely be appealed, which would be expected to take an additional 12-24 months to be resolved. Accordingly, the Company does not expect a final decision on the DPLTA appraisal proceedings to be rendered and published prior to 2027, and most likely not until 2028 or beyond.

Our obligation to pay Annual Recurring Compensation under the DPLTA is a continuing payment obligation, which will amount to approximately €7.8 million (or $9.0 million based on the current exchange rate) per year assuming none of the minority Adtran Networks shareholders were to elect Exit Compensation. The foregoing amounts do not reflect any potential increase in payment obligations that we may have depending on the outcome of ongoing appraisal proceedings in Germany. The Annual Recurring Compensation is due on the third banking day following the ordinary general shareholders’ meeting of Adtran Networks for the respective preceding fiscal year (but in any event within eight months following expiration of the fiscal year). With respect to the 2025 fiscal year, Adtran Networks’ ordinary general shareholders meeting is scheduled for the second quarter of 2026, and the Annual Recurring Compensation will be due on the third banking day following the meeting. During the three months ended March 31, 2026 and 2025, we accrued $2.2 million and $2.4 million, respectively, in Annual Recurring Compensation, which was reflected as an increase to retained deficit.

For the three months ended March 31, 2026, approximately 0.2 million shares of Adtran Networks stock were tendered to the Company and Exit Compensation of €3.6 million or approximately $4.1 million are to be settled in cash in April 2026. For the three months ended March 31, 2025, less thanone thousand shares of Adtran Networks stock were tendered to the Company and exit compensation payments of €12 thousandor $13 thousand based on the applicable exchange rates at the time of the transaction were paid to Adtran Networks shareholders.

In addition, under the DPLTA, subject to certain limitations pursuant to applicable law and the specific terms of the DPLTA, (i) the Company is entitled to issue binding instructions to the management board of Adtran Networks, (ii) Adtran Networks will transfer its annual profit to the Company, subject to, among other things, the creation or dissolution of certain reserves, and (iii) the Company will absorb the annual net loss incurred by Adtran Networks. The Company’s payment obligation in satisfaction of the requirement that it absorb Adtran Networks’ annual net loss applies to the net loss generated by Adtran Networks in 2025 and it will apply to any net loss generated by Adtran Networks in 2026.

Performance Bonds

Certain contracts, customers and jurisdictions in which we do business require us to provide various guarantees of performance such as bid bonds, performance bonds and customs bonds. As of March 31, 2026 and December 31, 2025, we had commitments related to these bonds totaling $22.2 million and $22.4 million, respectively, which expire at various dates through April 2029. In general, we would only be liable for the amount of these guarantees in the event of default under each contract, the probability of which we believe is remote.

Purchase Obligations

The Company purchases components from a variety of suppliers and uses contract manufacturers to provide manufacturing services for our products. Our inventory purchase obligations are for product manufacturing requirements, as well as for commitments to suppliers to secure manufacturing capacity. Certain of our inventory purchase obligations with contract manufacturers and suppliers relate to arrangements to secure supply and pricing for certain product components for multi-year periods. As of March 31, 2026, purchase obligations totaled $223.7 million.

Tariff Refund

On February 20, 2026, the U.S. Supreme Court issued a ruling striking down certain tariffs previously imposed under the International Emergency Economic Powers Act ("IEEPA"). The ultimate availability, timing, and amount of any potential refunds of such tariffs remain highly uncertain and are subject to further legal, regulatory, and administrative developments. Following the Supreme Court’s decision, the U.S. presidential administration announced its intention to invoke other laws to collect tariffs and announced new tariffs on imports from all countries, in addition to any existing non-IEEPA tariffs (including tariffs on semiconductors, which are expected to increase in June 2027).

The Company has concluded that the potential refund of IEEPA tariffs should be evaluated under a loss recovery model pursuant to Accounting Standards Codification ("ASC") 410‑30. The tariffs at issue were previously capitalized to inventory and subsequently expensed through cost of goods sold. Accordingly, any refund represents a recovery of previously recognized costs, and recognition is limited to amounts previously recorded.

Under the loss recovery model, an asset for recovery may be recognized only when receipt is considered probable, as defined under ASC 450‑20. While the Supreme Court ruling establishes a legal basis for recovery, material uncertainty remains regarding the administrative process required to obtain refunds. The U.S. Customs and Border Protection ("CBP") system became operational on April 20, 2026.

Given the lack of clarity surrounding refund execution to determine expected recovery amount, the Company has concluded that recovery of the IEEPA tariffs is not probable as of the reporting date. Accordingly, no refund receivable has been recognized. Management will continue to monitor developments, including CBP implementation milestones, formal guidance on claim submission, and claim acceptance processes.

Additionally, Adtran may owe money to customers depending on final assessments of contractual or implicit passthrough obligations. The Company will continue to monitor developments related to both refund recoverability and customer refund considerations and will update its accounting conclusions in future periods as facts and circumstances evolve.

401(k) Plan Corrective Action

In June 2024, the Company identified that within our Adtran, Inc. 401(k) plan for the year ended 2023, that deferrals and matching contributions should have been applied to vested equity award amounts in accordance with the plan documents. As such, we filed a voluntary correction program (“VCP”) application with the IRS and the Company is still in negotiations with the IRS regarding the appropriate corrective actions for this failure. Nonetheless, based on the current facts and circumstances surrounding the VCP negotiations, the Company accrued $1.4 million during the year ended December 31, 2025.