20 CFR 404.437: Excess earnings; benefit rate subject to deductions because of excess earnings.

We will further reduce your benefits (other than a disability insurance benefit) because of your excess earnings (see § 404.430), after your benefits may have been reduced because of the following:

(a) The family maximum (see §§ 404.403 and 404.404), which applies to entitled beneficiaries remaining after exclusion of beneficiaries deemed not entitled under § 404.436 (due to a deduction for engaging in non-covered remunerative activity outside the United States or failure to have a child in one's care);

(b) Your entitlement to benefits (see § 404.410) for months before you reach full retirement age (see § 404.409(a)) (this applies only to old-age, wife's, widow's, widower's or husband's benefits);

(c) Your receipt of benefits on your own earnings record, which reduces (see § 404.407) your entitlement (or deemed entitlement; see § 404.420) to benefits on another individual's earnings record; and

(d) Your entitlement to benefits payable (or deemed payable) to you based on the earnings record of an individual entitled to a disability insurance benefit because of that individual's entitlement to workers' compensation (see § 404.408).