A P800, also known as a tax calculation, is a letter from HMRC that tells you that you have paid the wrong amount of tax.

A P800 can show you:

• if you paid too much tax: HMRC will tell you that you’ll get a refund
• if you paid too little tax: HMRC will, of course, inform you about it and tell you how you can pay it.

If you receive a P800, you should check the details against your P60, P45 and P11D forms, to make sure that HMRC hasn’t made a mistake.