The average retired household loses 30% of their annual income to the taxman, according to new research.
In the 2011/2012 tax year, the average household gross income among the retired was £21,300 and £6,400 of it was paid to HM Revenue & Customs - or just over 30%.
Income tax, VAT and council tax accounted for the lion's share of the taxman's demands, according to analysis from Prudential.
Income tax and VAT each accounted for 8% of the average retired household's annual income, with council tax taking a 4% slice.
Other indirect taxes in addition to VAT - such as vehicle excise duty and those on alcohol, tobacco and petrol - accounted for a further 10% of gross income.
With all indirect taxation taking an 18% bite out of the average retired household's income, those on lower incomes are likely to find themselves paying out a greater proportion in tax.
A stark reminder
Stan Russell, retirement income expert at Prudential, said: "Previously our research has shown that retirees are becoming more optimistic about the income they expect to receive when they stop working. However, these latest figures are a stark reminder that not all the income you receive in retirement will be yours to spend as you like."
He added: "The best way to secure your desired level of retirement income is to save as much as possible as early as possible in your working life."