20 C.F.R. § 416.1323

(a) Effective date. Suspension of payments due to ineligibility for benefits because of excess income is effective with the first month in which “countable income” (see §§ 416.1100 through 416.1124 of this part) equals or exceeds the amount of benefits otherwise payable for such month (see subpart D of this part). This rule applies regardless of the month in which the income is received.

(b) Resumption of payments. If benefits are otherwise payable, they will be resumed effective with the first month in which a recipient's monthly countable income becomes less than the applicable Federal benefit rate (or the sum of that rate and the level for any federally administered State supplementary payment) for that month. If the reason that a recipient's benefits were suspended was excess income, the payment for the first month that benefits are reinstated will not be prorated under § 416.421.