20 CFR 217.3: Need to file an application.

In addition to meeting other requirements, a person must file an application to become entitled to an annuity or lump sum. Filing an application will—

(a) Permit a formal decision on whether the person is entitled to an annuity or lump sum;

(b) Protect a person's entitlement to an annuity for as many as 12 months before the application is filed; and

(c) Provide the right to appeal if the person is dissatisfied with the decision (see part 260 of this chapter).