Tax overpayments and underpayments

1. Your tax calculation

If you’re employed or get a pension, HM Revenue and Customs (HMRC) checks whether you’re paying the right amount of tax throughout the year.

They may adjust your tax during the year if your circumstances change, for example if you get a pay rise or a company benefit.

If you haven’t paid the right amount at the end of the tax year, HMRC will post you a P800 calculation. This will show you how to get a refund or pay tax you owe.

When you might get a P800

You might get a P800 if you:

  • finished one job and started a new one in the same month
  • started receiving a pension at work
  • received Employment and Support Allowance or Jobseeker’s Allowance

You won’t get a P800 if you’re registered for Self Assessment. Your bill will be adjusted automatically if you’ve underpaid or overpaid tax.

P800s are sent out after the tax year ends on 5 April. You’ll normally get yours by the end of October.

Checking your P800

Your P800 shows the income you should have paid tax on. This includes any income from pay, pensions, state benefits, savings interest and employee benefits.

Compare the figures with your records, for example your P60, bank statements or letters from the Department for Work and Pensions. If your state benefit was paid every 4 weeks, work out the total paid in a year by multiplying your regular payment by 13 (not 12).

You may be able to use the HMRC tax checker to work out how much tax you should have paid.

If you think your P800 is wrong

Contact HMRC if you think the amounts used on your P800 are wrong, or HMRC didn’t act on information you gave them.