ADTRAN Holdings, Inc.

ADTRAN Holdings, Inc. (the “Company”) is unable, without unreasonable effort or expense, to file its Quarterly Report on Form 10-Q for the quarter ended March 31, 2025 (the “Q1 Form 10-Q”) with the Securities and Exchange Commission (the “SEC”) within the prescribed time period for the reasons set forth below. As disclosed by the Company in its Current Report on Form 8-K filed with the SEC on May 13, 2025 (the “Form 8‑K”), which is incorporated herein by reference, the Company intends to restate its (i) consolidated financial statements as of and for the years ended December 31, 2024 (“Fiscal 2024”) and December 31, 2023 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 3, 2025, and (ii) unaudited condensed financial statements as of and for the interim periods ended March 31, 2024, June 30, 2024 and September 30, 2024 (the “2024 Interim Periods”) included in the Company’s Quarterly Reports filed with the SEC on May 10, 2024, August 9, 2024, and November 12, 2024, respectively. In addition, the Form 8-K disclosed that the Company’s management is evaluating the impact of this matter on its internal control over financial reporting as of December 31, 2024 and has identified at least one additional material weakness. Management had previously determined that its disclosure controls and procedures were not effective as of September 30, 2022 and all subsequent periods due to material weaknesses that were previously disclosed, which continues to be the case. The Company plans to restate, as soon as practicable, such financial statements (the “Restatements”). The Company does not expect the Restatements to set forth material changes to the financial information presented in the Preliminary Earnings Release, which was attached as an exhibit to a Current Report on Form 8-K furnished by the Company to the SEC on May 8, 2025 (the “Preliminary Earnings Release”)

ADTRAN Holdings, Inc. (the “Company”) is unable, without unreasonable effort or expense, to file its Annual Report on Form 10-K for the fiscal year ended December 31, 2023 (the “2023 Form 10-K”) with the Securities and Exchange Commission (the “SEC”) within the prescribed time period for the reasons set forth below. As disclosed in the Company’s Current Report on Form 8-K filed with the SEC on February 20, 2024 (the “February 20, 2024 Form 8-K”), the Audit Committee of the Board of Directors of the Company (the “Audit Committee”) concluded, after considering the recommendations of management, that the results attributable to the non-controlling interest and of the net loss attributable to the Company and, as a consequence, the loss per common share attributable to the Company, were materially misstated in (i) the Company’s unaudited condensed consolidated financial statements as of and for the quarter ended March 31, 2023 included in the Company’s Quarterly Report on Form 10-Q/A for the fiscal quarter ended March 31, 2023, (ii) the Company’s unaudited condensed consolidated financial statements as of and for the quarter and six months ended June 30, 2023 included in the Company’s Quarterly Report on Form 10-Q for the fiscal quarter ended June 30, 2023, and (iii) the Company’s unaudited condensed consolidated financial statements as of and for the quarter and nine months ended September 30, 2023 included the Company’s Quarterly Report on Form 10-Q for the fiscal quarter ended September 30, 2023, respectively (collectively, the “Non-Reliance Periods”), and that such financial statements should no longer be relied upon. As disclosed in the February 20, 2024 Form 8-K, the Company’s management is continuing to evaluate the impact of the misstatement to the Company’s internal control over financial reporting and expects to identify additional material weaknesses during the periods covered by such reports

ADTRAN Holdings, Inc. (the “Company”) is unable, without unreasonable effort or expense, to file its Quarterly Report on Form 10-Q for the quarter ended June 30, 2023 (the “Q2 Form 10-Q”) with the Securities and Exchange Commission (the “SEC”) within the prescribed time period for the reasons set forth below. As disclosed in the Company’s Current Report on Form 8-K filed with the SEC on August 10, 2023 (the “August 10, 2023 Form 8-K”), subsequent to the Company’s earnings call on August 8, 2023 and during the preparation of the unaudited condensed consolidated financial statements to be included in the Q2 Form 10-Q, the Company determined that the principal amount of indebtedness outstanding under the Company’s revolving credit facility with a syndicate of banks, including Wells Fargo Bank, National Association (“Wells Fargo”), of $200 million at June 30, 2023 were noncurrent liabilities in the Company’s consolidated balance sheet. Therefore, the outstanding Wells Fargo revolving credit facility balances for the following prior periods were misclassified and will be adjusted from current to noncurrent liabilities on the balance sheets as follows: $60.0 million as of September 30, 2022, $60.0 million as of December 31, 2022, and $180.0 million as of March 31, 2023. Furthermore, in connection with the restatement of the December 31, 2022 financial statements, the Company will also correct certain errors related to the presentation of deferred tax assets (“DTAs”) and deferred tax liabilities (“DTLs”) on the balance sheets that were previously assessed as immaterial errors and that had been corrected in the Company’s Form 10-Q for the quarter ended March 31, 2023. Neither the adjustment of credit facility balances nor the correction of the presentation of DTAs and DTLs have any impact on, or result in any change to, the Company’s reported statements of income (loss) or statements of cash flows