20 CFR 416.1330: Suspension due to failure to apply for and obtain other benefits.

(a) Suspension effective date. A recipient ceases to be an eligible individual or eligible spouse when, in the absence of a showing of incapacity to do so, or other good cause, he or she fails within 30 days after notice from the Social Security Administration of probable eligibility, to take all appropriate steps to apply for and, if eligible, to obtain payments such as an annuity, pension, retirement, or disability benefit, including veterans' compensation, old-age, survivors, and disability insurance benefit, railroad retirement annuity or pension, or unemployment insurance benefit. Benefit payments are suspended due to such ineligibility effective with the month in which the recipient was notified in writing of the requirement that he or she file and take all appropriate steps to receive the other benefits. See § 416.210(e).

(b) Resumption of payment. If benefits are otherwise payable, they will be resumed effective with the earliest day of the month on which the recipient takes the necessary steps to obtain the other benefits. See § 416.421.