Despite the complexity of the retirement process, most research treats it as an abrupt and one-way transition. Our study takes a different approach by examining retirement reversals (unretirement) and their predictors. Using the British Household Panel Survey (1991–2008), and following participants into Understanding Society (2010–2015), we undertake a survival analysis to investigate retirement reversals among Britons aged 50–69 years who were born 1920–1959 (N=2181). Unretirement was defined as: 1) reporting being retired and subsequently recommencing paid employment, or 2) beginning full-time work following partial retirement (the latter defined here as reporting being retired and working fewer than 30 hours per week). A cumulative proportion of around 25 per cent of participants experienced a retirement reversal after reporting being retired; about half of these reversals occurred within the first five years of retirement. Unretirement was more common for participants who were male, more educated, in better health, owned a house with a mortgage (compared to owning it outright), and whose partner was in paid work. However, unretirement rates were not higher for participants in greater financial need, whether measured as subjective assessment of finances or household income quintiles. These results suggest that unretirement is a strategy more often used by those who are already advantaged and that it has the potential to exacerbate income inequalities in later life.