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What are base years?

Excerpted from "Social Security Handbook". See the up-to-date, official Social Security Handbook at

705. What are base years?

Your base years are the years after 1950 up to the year of the first month you become entitled to retirement or disability insurance benefits. For a survivor's claim, the base years include the year of the worker's death. A year wholly contained in a period of disability is not included in the base years. Years partially within a period of disability are included.

Example: Mr. Clifford applied for retirement insurance benefits in October 1995. He is found entitled to a reduced benefit beginning October 1995, the month in which he is age 62 throughout the month. His base years for purposes of the initial computation of his benefit rate are the years 1951 through 1994, the year before the year in which he became entitled to benefits (1995). Since the elapsed years are 40 (1955 through 1994, the year before he attains age 62), the computation years are 35 (40 minus 5). To find the PIA, the earnings are averaged over the 35 highest of the base years 1951 through 1994 after the earnings are indexed. Mr. Clifford's PIA may be recomputed to take into account any earnings he had in 1995. This increase, if any, in his retirement insurance benefit will be effective January 1996. (See §722.)

Last Revised: Sep. 22, 2003

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