20 CFR §404.423

Deductions provided for in §§ 404.415, 404.417, and 404.421 (as modified in § 404.458) are made by withholding benefits (in whole or in part, depending upon the amount to be withheld) for each month in which an event causing a deduction occurred. If the amount to be deducted is not withheld from the benefits payable in the month in which the event causing the deduction occurred, such amount constitutes a deduction overpayment and is subject to adjustment or recovery in accordance with the provisions of subpart F of this part.