Guaranteed Minimum Pensions are a defined benefit underpin broadly equal to SERPS (the State Earnings Related Pension Scheme) which must be provided by schemes if they contracted out of SERPS. They were introduced with contracting out in 1978, and could accrue up to 5 April 1997 when contracting out arrangements were changed.

GMPs are unequal between men and women because women accrue them more quickly than men because the state pension age for women was lower at the relevant time. The rates of revaluation of GMP are different to the increases to GMP in payment opening up further scope for divergence between men and women.