NISOURCE INC

To the shareholders and the Board of Directors of NiSource Inc.

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of NiSource Inc. and subsidiaries (the "Company") as of December 31, 2023 and 2022, the related statements of consolidated income, comprehensive income, stockholders' equity, and cash flows, for each of the three years in the period ended December 31, 2023, and the related notes and the schedule listed in the Index at Item 15 (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2023 and 2022, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2023, in conformity with accounting principles generally accepted in the United States of America.

We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company's internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control — Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission and our report dated February 21, 2024, expressed an unqualified opinion on the Company's internal control over financial reporting.

Basis for Opinion

These financial statements are the responsibility of the Company's management. Our responsibility is to express an opinion on the Company's financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matters

The critical audit matters communicated below are matters arising from the current-period audit of the financial statements that were communicated or required to be communicated to the audit committee and that (1) relate to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matters below, providing separate opinions on the critical audit matters or on the accounts or disclosures to which they relate.

Non-Controlling Interest - Minority Interest Investment in NIPSCO Holdings II LLC – Refer to Notes 1, 4, 6, and 15 to the financial statements

Critical Audit Matter Description

On December 31, 2023, the Company consummated the closing of the issuance of a 19.9% equity interest in NIPSCO Holdings II LLC, a wholly-owned subsidiary of the Company and the sole owner of Northern Indiana Public Service Company LLC (“NIPSCO”), to BIP BLUE BUYER L.L.C., an affiliate of Blackstone Infrastructure Partners. At closing, BIP BLUE BUYER L.L.C., acquired a 19.9% equity interest in NIPSCO Holdings II LLC in exchange for making a capital contribution of $2.16 billion in cash to NIPSCO Holdings II LLC. Upon consummation of the minority interest transaction, the Company owns an 80.1% controlling indirect equity interest in NIPSCO LLC while BIP BLUE BUYER L.L.C., owns the remaining 19.9% indirect equity interest.

We identified the $2.16 billion minority interest investment in NIPSCO Holdings II LLC as a critical audit matter due to the significant degree of judgement involved in complex accounting and tax conclusions. This required a significant degree of auditor judgment when performing audit procedures, including the need to involve professionals in our firm with the appropriate expertise to assist us in evaluating management’s conclusions around the accounting and tax treatment for the transaction.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the minority interest investment in NIPSCO Holdings II LLC included the following, among others:

•We tested the effectiveness of controls over the accounting assessment for this transaction, including the controls over technical accounting conclusions and income tax treatment of this transaction.

•We evaluated management’s conclusions related to accounting for the transaction by:

▪Obtaining and reading the contractual agreements related to this transaction,

▪Involving professionals in our firm with the appropriate expertise in accounting for minority interest transactions to evaluate the work performed by management related to the accounting treatment of the transaction,

▪Involving professionals in our firm with the appropriate expertise in income taxes to evaluate the work performed by management related to the tax treatment of the transaction,

•We evaluated the appropriateness of the Company’s disclosures related to the minority interest investment, including balances recorded.

Regulatory Matters - Impact of Rate Regulation on the Financial Statements - Refer to Notes 1, 9, and 12 to the financial statements

Critical Audit Matter Description

The Company’s subsidiaries are fully regulated natural gas and electric utility companies serving customers in six states. These rate-regulated subsidiaries account for and report assets and liabilities consistent with the economic effect of the manner in which regulators establish rates, if the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates can be charged to and collected from customers. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income are deferred on the consolidated balance sheets and are later recognized in income as the related amounts are included in customer rates and recovered from or refunded to customers.

The Company’s subsidiaries’ rates are subject to regulatory rate-setting processes. Rates are determined and approved in regulatory proceedings based on an analysis of the subsidiaries’ costs to provide utility service and a return on, and recovery of, the subsidiaries’ investment in the utility business. Regulatory decisions can have an impact on the recovery of costs, the rate of return earned on investment, and the timing and amount of assets to be recovered by rates. The respective commission’s regulation of rates is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital. Decisions to be made by the commission in the future will impact the accounting for regulated operations, including decisions about the amount of allowable costs and return on invested capital included in rates and any refunds that may be required. While the Company has indicated it expects to recover costs from customers through regulated rates, there is a risk that the commission will not approve: (1) full recovery of the costs of providing utility service, or (2) full recovery of all amounts invested in the utility business and a reasonable return on that investment.

We identified the impact of rate regulation, specifically certain regulatory assets and liabilities at the Company’s Northern Indiana Public Service Company LLC and Columbia Gas of Ohio, Inc. subsidiaries, as a critical audit matter due to the significant judgments made by management to support its assertions about certain account balances and the significant degree of subjectivity involved in assessing the likelihood of recovery of incurred costs in current or future rates due in part to uncertainty related to future decisions by the rate regulators. This required specialized knowledge of accounting for rate regulation and the rate setting process due to its inherent complexities and a significant degree of auditor judgment when performing audit procedures to evaluate the reasonableness of management’s conclusions.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the application of specialized rules to account for the effects of cost-based rate regulation related to the uncertainty of future decisions by the rate regulators, specifically the Indiana Utility Regulatory Commission (IURC) and the Public Utility Commission of Ohio (PUCO), included the following, among others:

•We tested the effectiveness of management’s controls over (1) the evaluation of the likelihood of (a) the recovery of costs deferred as regulatory assets in future periods, and (b) regulatory developments that may affect the likelihood of recovering costs in future rates or of a future reduction in rates; and (2) the evaluation of Hypothetical Liquidation Book Value (HLBV) Models for the company’s Renewable Joint Ventures and its impact on the Company’s regulatory assets for recovery in rate base.

•We read relevant regulatory orders issued by the IURC and the PUCO, including regulatory statutes, interpretations, procedural memorandums, filings made by interveners, and other publicly available information to assess the likelihood of recovery in future rates or a future reduction in rates based on precedents of the commissions’ treatment of similar costs under similar circumstances. We evaluated the external information and compared to management’s recorded regulatory asset and liability balances for completeness, including the implementation of new rate orders at Northern Indiana Public Service Company LLC’s electric business and Columbia Gas of Ohio, Inc.

•For the Northern Indiana Public Service Company LLC gas base rate case proceeding, we inspected the Company’s and intervenors’ filings with the commissions that may impact the Company’s future rates, for any evidence that might contradict management’s assertions related to recoverability of recorded assets.

•We inquired of management about property, plant, and equipment that may be abandoned with an emphasis on the generation strategy related to Northern Indiana Public Service Company LLC’s R.M. Schahfer and Michigan City Generating Stations. We inspected minutes of the board of directors and regulatory orders and other filings with the IURC to identify evidence that may contradict management’s assertion regarding probability of an abandonment.

•We read the relevant regulatory orders issued by the IURC for the Company’s renewable energy investments. We evaluated the appropriateness of recognizing a regulatory liability or asset representing timing differences between the profit allocated under the HLBV method related to the consolidated joint ventures and the allowed earnings included in regulatory rates. We also evaluated the appropriateness of the offset to the regulatory liability or asset recorded in depreciation expense.

/s/DELOITTE & TOUCHE LLP

Columbus, Ohio

February 21, 2024

We have served as the Company's auditor since 2002.