HMRC has used the wrong state pension figure on some self-assessment tax returns, a mistake that could leave around 1.7 million pensioners paying too much tax unless they check their forms before filing. The error matters now because the self-assessment deadline is January 31 2027, and anyone affected still has time to correct the figure.
Steve Webb said the problem is worrying because HMRC appears to have been getting the state pension tax calculation wrong itself. The former pensions minister said the way the state pension is taxed is already a regular source of confusion, and the latest error risks adding to that for people who rely on HMRC to pre-fill their return accurately.
HMRC pre-populates the state pension section of self-assessment returns, but on some forms it has used 52 weeks at the higher current-year rate rather than the correct split of 51 weeks at the current rate and one week at the previous year’s rate. In most cases that mistake will amount to about £5, HMRC said, but the number of people affected is far larger than the sum involved would suggest.
The problem affects only a small share of the 13.2 million people receiving the state pension, because most recipients do not complete self-assessment at all. Those whose income comes only from the state pension, a workplace pension or savings interest usually do not need to file a return, and HMRC can normally collect any tax due automatically when income is limited to those sources. The issue is aimed at people who are self-employed or who earn rental income as buy-to-let landlords, and at others whose tax affairs are complex enough to require a return.
That is why the safest step for anyone filing this year is to compare HMRC’s pre-filled figure with the DWP uprating letter sent before the start of the 2026-27 tax year, which sets out the new weekly state pension rate. If the number is wrong, it can be overwritten on the form before January 31 2027. HMRC said anyone who believes the amount shown is incorrect can amend it before submitting, and anyone who thinks they have already overpaid can ask for a repayment.
The awkward part is that the error sits inside a system built to remove exactly this sort of mistake. If a pensioner has a private pension, the provider usually deducts tax for both the private and state pensions through the tax code, while the state pension still appears on self-assessment as a gross figure in its own section. That makes the wrong number easy to miss and, for those who already filed, easy to carry forward unless they go back and amend the return or contact HMRC directly for a refund.
HMRC has apologised to those affected and said the tax difference is small, but the scale of the error means a lot of people may still be owed money. For now, the key question is not whether the sums are large — they are not — but how many taxpayers have already filed using the wrong figure and will need to put it right before the deadline.
