Under the Treasury Notice, eligibility is based only on whether Social Security taxable wages for each pay period are under $4,000 for a biweekly pay period or an equivalent amount with respect to other pay periods. No annual wage limit applies.
The $4,000 biweekly limit is applied on a pay period by pay period basis. If the amount of Social Security taxable wages payable to an employee for one specific pay period is less than the corresponding threshold amount (e.g., $4,000 biweekly), the employee Social Security taxes for that pay period are eligible for deferral regardless of the amount of wages or compensation paid to the employee for any other pay period.