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Why you receive a P800 tax calculation

At the end of every tax year your employer or pension provider sends HMRC details of how much income you have received and the tax you have paid during the year.

If you haven't paid the right amount of tax, you'll receive a P800 tax calculation telling you what HMRC considers the correct amount to be and whether you have paid too much or too little.

Checking your P800 tax calculation

You need to check the entries on your P800 tax calculation carefully to make sure all your income and any benefits or expenses you get are listed and the amounts are correct. You also need to make sure your tax allowances are correct.

HMRC may not have all the information they need to calculate your tax correctly, for example because your circumstances have changed, so it's really important you check your calculation to make sure the information in it is complete and correct.

Use the following items to help you:

• form P60 - you get this at the end of each tax year
• form P45 - you get this when you leave a job
• PAYE Coding Notice
• P11D Expenses and benefits
• P9D Expenses payments and income from which tax cannot be deducted
• bank and building society statements

The notes 'P800 Notes - Understanding your P800 tax calculation' that you receive with your P800 tax calculation explain each section of the calculation - so it's a good idea to read them carefully as well. They'll help you check if the information in the calculation is correct and understand why you have paid too much or too little tax.

• Download 'Understanding your tax calculation - P800 notes (PDF, 124K) Opens new window

• Help with PDF files

• Tax and National Insurance on company benefits

• Expense payments in your tax code

• Introduction to tax allowances and reliefs

If your employer or pension provider has not deducted enough tax

Most employers and pension providers deduct the right amount of tax from your pay or pension. But sometimes they make mistakes. If you think your employer or pension provider has made a mistake - for example because they didn't take reasonable care to use the right tax code - they may be due to pay back the tax owed instead. Find out more by following the link below.

• Download 'Employer errors in deduction of Pay As You Earn tax' (PDF, 36K) Opens new window

• Help with PDF files

If you think this may apply to you, write to HMRC at the address shown on your P800 tax calculation telling them why you think your employer or pension provider has made a mistake.

HMRC will tell you as soon as possible what they have decided and what this means for you.

If HMRC received information relevant to your tax calculation but didn't use it

If you think HMRC should have already collected the tax due because you or a third party had provided all the relevant information - but HMRC has not used it or delayed using it - then in some limited circumstances HMRC may agree that you don't have to pay it back.

For example, you started receiving the State Pension and the Department for Work and Pensions sent HMRC information about this but HMRC delayed using it and it was reasonable for you to think that your tax affairs were in order. Find out more by following the link below.

• HMRC delays in using information Opens new window

If you think this may apply to you, contact HMRC using the address or telephone number shown on your P800 tax calculation. They will decide whether you have to pay back the tax they have asked you for.

If you've paid too much tax

If you agree that your P800 tax calculation correctly shows all your income, benefits and allowances you don't need to do anything with it but keep it safe.

Usually, you'll receive your refund by cheque within 14 working days of the date on your P800 tax calculation.

If you don't agree with something in your P800 tax calculation please read the section 'What to do if you think your P800 tax calculation is wrong'.

If you've paid too little tax

If you agree that your P800 tax calculation correctly shows all your income, benefits and allowances you don't need to do anything with it but keep it safe.

If you don't agree with something in your P800 tax calculation read the section 'What to do if you think your P800 tax calculation is wrong'.

Paying back the tax you owe

If your P800 tax calculation says that HMRC will include any underpaid tax in your tax code for the next tax year, you will pay it back in equal instalments over one year along with your normal tax deductions from your pay or pension. For example, if you didn't pay enough tax in the tax year 2010-11, you'll pay back the amount you owe in the tax year 2012-13, which starts on 6 April 2012.

You'll get your new tax code early in 2012. In the meantime you don't need to do anything more.

• How underpayments of tax affect your tax code

If your P800 tax calculation does not say that HMRC will include any underpaid tax in your tax code, HMRC will write to you about how to pay. If you would prefer to pay now contact HMRC by using the telephone number or address on your P800 tax calculation.

If you can't afford to pay the tax you owe

If you think you can't afford to pay the amount you owe or paying it through your tax code over one year would cause you financial difficulty, contact HMRC using the address or telephone number shown on your P800 tax calculation to discuss options for paying. You might be able to spread the payments over two or three years.

If you are on means-tested benefits

If you are on means-tested benefits, the way you pay back tax could affect your entitlement. You might want to take advice on this before agreeing to pay by cheque - for information on where to get help and advice see the section 'Getting help or advice' towards the end of this guide. If your 'net income' - income after tax has been taken off - changes or your capital goes down as a result of you paying back tax, tell your benefits provider.

This will not affect any tax credits you get as they are based on income before tax is deducted.

If you receive more than one P800 tax calculation

If you receive more than one P800 tax calculation the amount of tax you have overpaid or underpaid in the earlier tax year is carried forward to the later tax year. This means you get a final figure of tax overpaid or underpaid for the two years. The amount carried forward from the earlier year is shown on your P800 tax calculation for the later year in the 'adjustments' box under the heading 'less other adjustments'.

For example, you underpaid tax of £400 in 2009-10 and overpaid tax of £500 in 2010-11. Your P800 tax calculation for 2010-11 includes the £400 carried forward from 2009-10 and subtracts this amount from the £500 you overpaid in 2010-11. Your refund of £100 (£500 minus £400) is shown as the final result.

Receiving your refund

You'll receive one refund for the total amount of tax you have overpaid in the tax years covered by your P800 tax calculations.

What to do if you think your P800 tax calculation is wrong

If you don't agree with something included in your P800 tax calculation, contact HMRC using the telephone number or address provided. The telephone number is 0845 300 0627. If HMRC agrees that your P800 tax calculation is incorrect they will amend it and send you a new one.

Telling HMRC about changes that might affect your tax

It's important you tell HMRC about any changes in your circumstances that could affect the amount of tax you pay so that you don't end up paying the wrong amount. Find out more about the changes you need to report and how to report them by following the link below.

• Reporting changes that might affect your tax

Getting help or advice

If you need advice or more information a number of voluntary organisations may be able to help you - or you could consult a professional adviser (though bear in mind there may be a charge). If you have debts, there are many organisations offering free and independent debt advice over the phone or face to face.

• Free help and advice contacts

• Debt - where to get free help and advice

More useful links

• Download 'Understanding your Tax Calculation - P800 Notes' (PDF, 124K) Opens new window

• Download 'P800 Additional notes' (PDF, 51K) Opens new window

• Help with PDF files

• Income Tax rates and allowances Opens new window

• Income Tax - the basics

• Tax codes

• How to correct mistakes in your tax

• Quick check tax calculator Opens new window

• How to complain to HM Revenue & Customs

• Your Charter - what you can expect from HMRC and what they can expect from you Opens new window