How does HM Revenue and Customs know what allowances I'm entitled to?

If you have already completed a Self Assessment tax return, HM Revenue and Customs may have the information it needs. HMRC may send you a review form at the end of the tax year. This is a single page form that allows HMRC to check your income details and any allowances and expenses you are entitled to. It is called a P810.

It is important to send your P810 back, so that your tax code can be checked, and any changes made if necessary. It will also help to ensure you are given the full tax-free allowances you are due.

If your circumstances have changed – you get married or become self-employed, for example – and you have not reported these on the forms mentioned above, or you have completed a form, but the changes have not been reflected in your notice of coding, it is important to tell HMRC. This will help you avoid paying too much or too little tax by the end of the tax year.

Note: This content is provided as general background information and should not be taken as legal advice or financial advice for your particular situation. Make sure to get individual advice on your case from your union, a source on our free help page or an independent financial advisor before taking any action.