The earliest you can claim the State Pension is when you reach your State Pension age (SPA), you can claim it whether or not you are still in employment. Your SPA depends on when you were born, you can check it on the GOV.UK website.. The right to claim certain benefits changes once you reach State Pension Age (SPA).
Until December 2018, the SPA for men remains at 65, but will begin rising after that (see below).
The SPA for women, which until 2010 was 60, is going up to 65 (64 and six months from April 2018 and 65 from November 2018). Because of the way the increase was brought in, affecting women born in the early 1950s, many experienced financial hardship, with not enough time to re-plan, and there is a campaign (WASPI) for fair transitional State Pension arrangements.
From December 2018 the State Pension age for both men and women starts to increase beyond 65, reaching 66 by October 2020 (for men and women born on or after 6 October 1954).
SPA is due to rise to 67 between 2026 and 2028 (for men and women born on or after 6 March 1961). Under the current law, the State Pension age is due to increase to 68 between 2044 and 2046, but the government has announced proposals to bring this timetable forward so that the SPA would increase to 68 between 2037 and 2039.