Last Reviewed: November 2023

Paying the tax you owe is supposed to be simple—and for many people, it is. If you’re working ‘on the books’ for an employer, it’s all handled automatically through the Pay As You Earn (PAYE) scheme. If you’re self-employed or have other untaxed income, though, you’ll use the Self Assessment tax return system to report your earnings and expenses to the taxman. Either way, HMRC crunches the numbers and works out how much tax you owe. After that, the money’s either taken from your pay before you get it or you settle up yourself.

Here’s where the problems start. HMRC’s calculations are only as reliable as the information it’s working with. The taxman won’t always have a complete and accurate picture of your work and finances. When that happens, it’s easy to end up paying the wrong amount of tax without realising it – often for years at a time! There are millions of pounds in overpaid tax going unclaimed every year, and you may need to apply for a tax overpayment refund to get it back.
For example, you might be owed a tax overpayment refund if: