As is frequently the case, it began when someone noticed something didn’t add up. Mike Warburton, a former tax director who worked at Grant Thornton for many years, looked at the state pension box while he was sitting in front of his own online self-assessment return. The completed figure didn’t look right. Not significantly incorrect. A man who has read tax laws for a living couldn’t let it go because it was just wrong enough.
After sending a few emails to the HMRC press office, he discovered something almost ridiculous. A state pension figure calculated at 52 weeks of the new, higher pension rate had been pre-populated into the returns of about 1.7 million pensioners by the tax authority. The correct amount is one week at the old rate plus fifty-one weeks at the new one, according to HMRC’s own published guidance (see page seven, if you’re interested). In other words, the system was at odds with the handbook that was right next to it.
There is a feeling that this occurred as a result of the quiet dysfunction that develops between big institutions rather than out of malice. The Department for Work and Pensions provided the figures, but they had determined entitlement in a different way. Warburton believes this is because the 2025–2026 tax year started on a weekend, which moved the calculations forward by one week. HMRC immediately included the DWP’s figure in people’s returns. It doesn’t seem like anyone looked to see if it complied with the law. It’s the kind of thing that only comes to light on a typical afternoon when someone with the appropriate training carefully examines their own paperwork.
The sums in question are modest. The apology, when it was made, mainly relied on the fact that, according to HMRC, the difference is typically about £5. “We apologise to those affected by this calculation error, although the impact is small,” a spokesperson said. A round of coffee is hardly worth five pounds. However, it’s difficult to ignore how quickly “small” came to be the key term, as though the magnitude of the mistake resolved the issue of whether it was significant.
Steve Webb, a former pensions minister and partner at pension consultants LCP, identified the unease. He pointed out that the way the state pension is taxed is already a common source of confusion for regular people, and it is extremely concerning that the tax authority seems to have been making mistakes as well. That’s the part that stays. The more complex cases—self-employed people, buy-to-let landlords, and those already struggling with forms most of us never see—are the pensioners caught up in this. They are supposed to identify and fix a bug that was introduced by the government’s own software.
According to HMRC, anyone who believes the amount is incorrect can change it before filing, and those who have already overpaid can request a refund. Alright. However, it did not promise to fix the pre-populated numbers themselves, which seems like a more sincere solution. There is still time, as the deadline for online returns for the recently concluded year is January 31, 2027.
The £5 doesn’t stay with you. It serves as a reminder that automation silently, at scale, inherits whatever presumptions are fed into it. We all make mistakes, and how we respond to them is what counts, as Warburton succinctly stated. HMRC expressed regret, which is a step in the right direction. It’s still unclear if it truly fixes the box.
