SEC Form 11-K filed by ADTRAN Holdings Inc.

Note 1 – Description of the Plan

The following description of the ADTRAN, Inc. 401(k) Retirement Plan (the “Plan”) provides only general information. Participants should refer to the Plan document and summary Plan description for a more complete description of the Plan’s provisions.

General

ADTRAN Inc. (the “Company” or the “Employer”) adopted the Plan on January 1, 1990 to provide certain retirement benefits for eligible employees (as outlined below). The Plan is a defined contribution plan subject to the provisions set forth in the Employee Retirement Income Security Act of 1974 (“ERISA”) and the provisions of Internal Revenue Code of 1986, as amended, (the “IRC”) Sections 401(a) and 401(k). The Plan assets are held by Fidelity Management Trust Company (“Fidelity”), which executes investment transactions, receives the Plan contributions, credits participants' individual accounts and pays benefits to participants and their beneficiaries in accordance with the provisions of the Plan.

The Company became a wholly-owned subsidiary of ADTRAN Holdings, Inc. on July 8, 2022 (the “Effective Date”). Each share of ADTRAN, Inc. common stock issued and outstanding immediately prior to the Effective Date was canceled and automatically converted into and became the right to receive one share of common stock, par value $0.01 per share, of ADTRAN Holdings, Inc..

Eligibility

All regular, full-time employees are eligible to participate in the elective deferral portion of the Plan immediately upon hire, and in the safe harbor matching portion of the Plan beginning on the employee’s one-year anniversary date of service, except leased employees, and nonresident aliens without income in the United States (the “U.S.”). Interns and seasonal employees may participate after attaining age 21 and completing 1,000 hours of service.

The Plan includes an automatic enrollment provision where an initial pre-tax deferral contribution of 5.00% of eligible compensation will be made for newly eligible employees, participant loans will no longer be due immediately upon termination but rather will be payable in accordance with the provisions of the loan note and the costs to administer the Plan may be paid from forfeitures, if any.

Contributions

The Plan allows for pre-tax or Roth contributions of up to 60% of a participant’s eligible compensation, as defined in the Plan document and subject to annual limitations established by the Internal Revenue Service (the “IRS”). The Plan also allows eligible participants who are age 50 or over to make additional deferrals. Participants may change their contribution deferral election under the Plan each pay period.

Under the terms of the Plan, the Company is required to make safe harbor matching contributions of 100% of an eligible participant’s first 3% of contributions and 50% of the next 2% of contributions, subject to certain limits. Additionally, the Plan offers an after-tax option that's limited to a 5% cap on employee contributions.

Participant Accounts and Investment Options

Each participant’s account is credited with the employee’s contribution and the Company’s matching contribution for that employee, when applicable, plus an allocation of Plan earnings. Allocations of Plan earnings are based on account balances and underlying investments within each participant’s account, as defined more fully in the Plan document. Each participant directs how contributions made to the Plan on his/her behalf are to be invested among the investment options available under the Plan. The Plan currently offers 40 investment options, including the Company stock fund. Total investment balances in the Plan for participants are limited to 20% of the Company stock fund.

The Plan also includes Fidelity Brokerage Link, which is a self-directed brokerage account that allows participants to invest in a broad range of securities, including stocks, bonds, mutual funds, exchange-traded funds, certificates of deposit and other investment choices.

Vesting

Retirement Date

The normal retirement date is the first day of the calendar month following the date a participant reaches age 62. Early retirement is permitted on the first day of the calendar month after a participant reaches age 59-1/2.

Note 2 – Summary of Significant Accounting Policies

Note 3 – Related Party and Party-In-Interest Transactions

The Plan allows for transactions with certain parties who may perform services or have fiduciary responsibilities to the Plan, including the Company. The Plan invests in shares of mutual funds or commingled trust funds managed by an affiliate of Fidelity, a subsidiary of which is the trustee of the Plan. These transactions qualify as party-in-interest transactions.

The Plan invests in common stock of the Company and issues loans to participants, which are secured by the balances in the participants’ accounts. During the year ended December 31, 2025, the Plan purchased 25,655 shares of the ADTRAN Holdings, Inc. Common Stock Fund for $209,920 and disposed of 31,017 shares for $266,895.

Fidelity Investments provides certain administrative services to the Plan pursuant to the Fidelity Investments Retirement Plan Service Agreement (the “Agreement”) between the Company and Fidelity Investments. The Company receives revenue credits from Fidelity Investments, which result from revenue-sharing agreements from the Plan’s investments. This revenue is reported as other income and may be applied as payment of administrative expenses incurred by the Plan or allocated back to participant accounts. Revenue sharing receipts of $182,373 were used to pay investment advisory fees during the year ended December 31, 2025. Revenue sharing account funds of $371,954 were allocated back to participant accounts during the year ended December 31, 2025. Unallocated revenue sharing account balances totaled $193,073 and $149,141 at December 31, 2025 and 2024, respectively.

Note 4 – Income Tax Status

The Plan obtained its latest opinion letter on June 30, 2020 from the IRS stating that the Plan, as then designed, was in compliance with the applicable requirements of the IRS. The Plan has subsequently been amended to conform with regulatory requirements and for minor administrative items. The Plan Administrator believes the Plan is designed and is currently being operated in compliance with the applicable provisions of the IRC. Accordingly, no provision for income taxes has been recorded in the Plan's financial statements.

U.S. GAAP requires Plan management to evaluate tax positions taken by the Plan and recognize a tax liability or asset if the Plan has taken an uncertain tax position that more likely than not would not be sustained upon examination by the IRS. The Plan Administrator has analyzed the tax positions taken by the Plan and has concluded that as of December 31, 2025, there are no uncertain tax positions taken or expected to be taken that would require recognition of a liability or asset or disclosure in the financial statements. The Plan is subject to routine audits by taxing jurisdictions; however, there are currently no audits for any tax periods in progress.

Note 5 – Reconciliation to Form 5500

Note 6 – Risks and Uncertainties

The Plan participants invest in various types of investment securities. Investment securities are exposed to various risks such as interest rate, market and credit risks. Due to the level of risk associated with certain investment securities and the level of uncertainty related to changes in the value of investment securities, it is at least reasonably possible that changes in risks in the near term could materially affect participants' account balances and the amounts reported in the Statements of Net Assets Available for Benefits and the Statement of Changes in Net Assets Available for Benefits.

Note 7 – Fair Value Measurements

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