The number of taxpaying pensioners has nearly doubled since the mid-1990s, a Freedom of Information Act request has revealed.
An FOIA request to HM Revenue and Customs by Royal London shows the growing tax bills faced by pensioners in different parts of the country.
Between the mid-1990s and the mid-2010s the number of taxpayers over the age of 65 nearly doubled from 3.3m in 1995-96 to 6.5 million in 2015-16.
It is estimated that the number has broadly stabilised since then, and stands at around 6.4 million in 2018-19.
Analysis of the data relating to nearly 7m taxpayers over state pension age in 2015-16 shows the average annual tax bill is £3,522.
For the 3.87m men the average bill is £4,341 and for the 3m women the average is £2,467.
More than a quarter of taxpaying pensioners are still in paid work. 1.5m have employment income and 500,000 have income from self-employment.
Royal London director of policy Steve Webb says: “Many people might assume that once you retire you cease to be of interest to the taxman. But these figures show that this is very far from being the truth.
“The number of taxpaying pensioners has nearly doubled in the last two decades. With talk of also requiring pensioners to pay National Insurance on any earnings or even pensions, the older population may start thinking of themselves as ‘Generation still taxed’.
“When planning for retirement it is vital to remember that the tax office will still want a slice of your income, which reinforces the need to put aside enough to secure a decent standard of living, even after the tax man has had his slice.”