A P800 is a tax calculation letter.
It tells a taxpayer, based on HMRC end of year review, that they have either paid too much or too little tax for a tax year.
After the tax year ends, HMRC PAYE records to check the correct amount of tax has been paid based on the information HMRC hold. Based on this information, a P800 is issued.
For the 2025 to 2026 tax year, HMRC expect to check around 45 million customer accounts, which will take until November 2026. HMRC say they have started issuing P800 letters,
Overpayments and underpayments
Where too much tax has been paid a taxpayer is able to claim a repayment. These letters will be issued first.
Where too little tax has been paid, HMRC will collect the outstanding amount automatically if the taxpayer:
- pays income tax through an employer or pension provider;
- earns enough income over their personal allowance to cover the underpayment;
- owes less than £3000 in tax.
Many customers can claim their repayment online or via the HMRC app and so we expect fewer calls about overpayments than underpayments. In some instances, the P800 will say that we will send the customer a cheque. In these circumstances the customer does not need to contact us as the cheque will be issued automatically.
Agents may see an increase in client queries during the summer and autumn months, from clients who want to know what the letter means and what to do next.
HMRC wants you to know what to expect. They do not say what to do if it is wrong.
