For years before 1978, a QC is any calendar quarter beginning January 1, April 1, July 1, or October 1, in which we paid an individual at least $50 in wages, or credited them with at least $100 of self-employment income (SEI).

SSA credits QCs on wages paid to an individual after 1936, or on SEI for taxable years beginning after 1950.  We may use military service wage credits, or railroad compensation to establish the QCs.