20 C.F.R. § 220.162

(a) General. Any annuitant receiving an annuity based on disability must report to the Board any work and earnings as described in §§ 220.160 and 220.161. The report may be a written or oral statement by the annuitant, or a person acting for the annuitant, made or sent to a representative of the Board. The report should include the name and address of the railroad or non-railroad employer, a description of the work and the amount of gross wages (before deductions) or the net income from self-employment (earnings after deducting business expenses).

(b) Employee reports. In addition to the requirement described in (a), a report of earnings over $400 a month must be made before the employee accepts a disability annuity (the annuity payment is issued and not returned) for the second month after the first month in which earnings are over $400. Along with the report, the employee must return the annuity payment for any month in which he or she earns over $400.