20 CFR 225.30 - General.
(a) A delayed retirement credit (DRC) is a percentage increase in a PIA. An employee who would have an insured status in accordance with section 214(a) of the Social Security Act based on combined railroad and social security earnings can earn DRC's. A DRC can be earned by the employee for each month, in or after the month of attaining full retirment age and before the month of attaining age 70 (72 before 1984), in which the employee does not receive either -
(2) The tier I and vested dual benefit work deduction annuity components or the social security overall minimum annuity rate because they are not paid since the employee works and has earnings in excess of the exempt amount. (The tier I and vested dual benefit work deduction annuity components, the social security overall minimum annuity rate and the exempt amount are described in parts 226, 229 and 230 of this chapter, respectively.)
(b) Any credit earned by the employee also extends to the employee's widow(er), remarried widow(er) or surviving divorced spouse when he or she receives a survivor annuity that is based on age or disability.