20 CFR 404.446 : Employees' Benefits (§ 1.1 To Parts 1011-1099) — (Part 400 To Part 499) — Social Security Administration (Part 400 To Part 499) — Federal Old-Age, Survivors And Disability Insurance (1950- ) (§ 404.1 To § 404.2127) — Deductions; Reductions; And Nonpayments Of Benefits (§ 404.401 To § 404.480) — Definition of “substantial services” and “services.”