We examine individuals’ retirement behaviour in response to changes in the State Pension eligibility age (SPe-age) introduced in UK Pension Acts. Our findings show that the annual probability of retirement reduced significantly in response to a one-year increase in SPe-age, by 8.2pp and 6.4pp for men and women, respectively. They also show that younger individuals can adjust their Expected Age of Retirement (EAR) downwards in response to an increase in their SPe-age. Thus, while an increase in the SPe-age induces individuals to postpone actual retirement, it does not necessarily lead to certain groups of individuals to revise their EAR upwards, which could result in suboptimal retirement planning. The latter can be problematic for those with low occupational pension wealth and/or individuals who rely disproportionately on State Pension. Our findings suggest the need for targeted communication campaigns aimed at specific groups of prime aged workers to improve their retirement planning.