A guide to claiming back Income TaxIt is not uncommon to overpay income tax, and this guide will help you get it back.HMRC use this information to calculate the exact amount of tax you should have paid, and often will refund any overpayment automatically.Once you do receive it, check it carefully as sometimes HMRC don’t have all the information and may have missed something.Claiming on-line If you haven’t received a P800, but suspect that you may have overpaid your tax, and you are registered with HMRC on-line, you can make your claim HERE.You can also claim back for previous years’ overpaid tax.