X0306 4/A 2021-11-17 2021-11-19 0 0000926282 ADTRAN INC ADTN 0001191219 STANTON THOMAS R C/O ADTRAN 901 EXPLORER BLVD. HUNTSVILLE AL 35806 1 1 0 0 Chairman and CEO Phantom Stock 2021-11-17 4 F 0 1330 20.91 D Common Stock 1330 156190.443 D On November 19, 2021, the reporting person filed a Form 4 which inadvertently omitted the withholding of taxes in connection with the vesting of performance shares awarded pursuant to a grant on November 9, 2018 under the ADTRAN, Inc. 2015 Employee Stock Incentive Plan. Each share of phantom stock represents a right to receive one share of common stock at the cash value thereof. The phantom stock becomes payable six months after the reporting person's separation of service with the Company. The reporting person may transfer the phantom stock account into an alternative investment at any time. This inadvertent error caused the Number of Derivative Securities Beneficially Owned Following Reported Transaction in Column 9 in the Form 4 filed by the reporting person on December 2, 2021 to be overstated by 1,330 shares. Michael Foliano, by power of attorney 2021-12-07