ADTRAN Holdings, Inc.

(a) Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

On November 3, 2025 (the “Termination Date”), in an effort to streamline the benefits offered to members of management and other key employees, the Company terminated its Deferred Compensation Program for Employees (the “Deferred Compensation Plan”) and its Equity Deferral Program for Employees together with the Deferred Compensation Plan, the “Plans”). The Plans are deferred compensation plans that have provided certain members of management or highly compensated employees, including certain of our named executive officers, with an opportunity to defer the receipt of a portion of their cash compensation, bonus, or other specified compensation. Each of the Plans has been maintained as an unfunded, nonqualified plan providing benefits based on the participant’s notional account balance at the time of retirement or separation, death or (with respect to the Deferred Compensation Plan) a change in control. The Company has also terminated its deferred compensation plans for its non-employee directors.

In accordance with Section 409A of the Internal Revenue Code of 1986, as amended, and as a result of the termination of the Plans, the payment of all benefits to each Plan’s participants and beneficiaries in the form of lump sum or installment distributions is scheduled to occur no earlier than twelve (12) months and no later than twenty-four (24) months following the Termination Date (the “Liquidation Date”). Distributions of amounts that are set to occur prior to the Liquidation Date will be made as scheduled under the terms of each Plan. Until the Liquidation Date, each of the Plans will continue to operate in the ordinary course, except that no new deferrals will be credited to the participants for compensation earned after the Termination Date.

(b) Not applicable

(c) Insider Trading Arrangements

During the fiscal quarter ended September 30, 2025, none of the Company’s directors or executive officers adopted or terminated any contract, instruction or written plan for the purchase or sale of Company securities that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) or any “non-Rule 10b5-1 trading arrangement.”