20 C.F.R. § 404.436
Excess earnings; months to which excess earnings cannot be charged because individual is deemed not entitled to benefits
Under the annual earnings test, excess earnings (as described in § 404.430) are not charged to any month in which an individual is deemed not entitled to a benefit. A beneficiary (i.e., the insured individual or any person entitled or deemed entitled on the individual's earnings record) is deemed not entitled to a benefit for a month if he is subject to a deduction for that month because of:
(a) Engaging in noncovered remunerative activity outside the United States (as described in §§ 404.417 and 404.418); or
(b) Failure to have a child in his or her care (as described in § 404.421).