Source
20 CFR § 416.420
Scoping language
Benefits shall be determined for each month. The amount of the monthly payment will be computed by reducing the benefit rate (see 416.410, 416.412, 416.413, and 416.414) by the amount of countable income as figured under the rules in subpart K of this part. The appropriate month's countable income to be used to determine how much your benefit payment will be for the current month (the month for which a benefit is payable) will be determined as follows: