What is a tax calculation?
A tax calculation is created by HMRC if you have not paid the right amount of tax. HMRC’s annual reconciliation of PAYE for the tax year 2020-21 is now almost complete. HMRC use salary and pension information to calculate if you have paid the correct amount of tax.
The tax calculation is usually generated automatically by HMRC’s computer systems on what is known as a P800 form. P800s are generally sent out from after the end of the tax year and the process is generally completed by the end of November. The P800 form is also used if you have not paid enough tax so be sure to read the document carefully.
If you are due a refund, the P800 form will usually tell you that you can claim a refund online. Once you complete the claim online, the refund will be paid within 5 working days and will be in your UK account once your bank has processed the payment. If you do not claim the refund online within 45 days, HMRC will send you a cheque.
If your P800 tells you that you will be repaid by cheque, then you do not need to take any further action and you should receive a cheque within 14 days of the date on the P800 Tax Calculation.
If you have not received a P800 form but think that you have overpaid tax, you can contact HMRC to inform them. If HMRC agree that you are due a tax refund they will send you a P800 form.
If you complete a Self-Assessment return, then you should not expect to receive a P800 form as any underpayment or overpayment of tax will be handled by way of your tax return.
Source: HM Revenue & Customs | 22-11-2021