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If you've made an error, missed something off your tax return or think you've paid the wrong amount of tax you may still be able to sort it out. If HM Revenue & Customs (HMRC) accept your new figures, you'll receive a repayment or be told how much extra tax to pay.
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If you make a mistake on your tax return you've normally got 12 months from 31 January after the end of the tax year to correct it. This is called an 'amendment'. For example, for the 2010-11 return you have until 31 January 2013 to make an amendment.
You can only amend your return after this date if you received your return late (after 31 October). In this case you must correct any mistakes within 12 months of the deadline for sending your return back.
If you sent your tax return on paper, you don't need to send in the whole tax return again. Just write to HMRC and attach the return pages that you want to change, clearly marked 'amendment'. You'll find the address on your tax return, your tax calculation or your Self Assessment Statement.
If you sent your tax return online it's easier if you make the amendment online too.
Log in to Self Assessment Online
If you think a refund is due you'll need to tell HMRC how you'd like to receive it.
For convenience you can have it deducted from any tax due on your next Self Assessment Statement if either:
Or you can ask for one of the following:
Sometimes HMRC may ask you for more information - to make sure that the figures are correct - before making a repayment.
If you owe more tax as a result of the changes to your tax return, HMRC will tell you how much you need to pay and when and how to pay it.
If you want to tell HMRC about a mistake after 12 months, it's too late to amend your return. You have to write to HMRC and tell them about the mistake instead.
In most cases, you'll get the tax you've overpaid back, as long as you claim it in time.
You must make a claim within four years of the end of the tax year that you're claiming for. For example if you paid too much tax in the 2007-08 tax year, you must make a claim by 5 April 2012.If you don't make a claim within the time limit you'll miss out on any repayment due.
You must make your claim in writing and it should include:
Sometimes HMRC may ask you for more information - to make sure that the figures are correct - before making a repayment.
For convenience you can have the repayment deducted from any tax due on your next Self Assessment Statement if either:
Or you can ask for one of the following:
If you owe more tax as a result of a mistake you've made, you should provide as much detail as possible when you tell HMRC. HMRC will work out the amount due and ask you to make a payment. Depending on the circumstances, you may have to pay interest on the amount due.
If you pay tax late or receive a repayment late, HMRC will add on any interest that's due. The rates of interest vary - you can find the current rate using the link below.
To get more help you can contact your HMRC office or ring the Self Assessment Helpline.
Contact the Self Assessment Helpline
If you do not complete a Self Assessment tax return but want to claim a tax refund, follow the link below to find out how.
Tax refunds and reclaiming overpaid tax
Self Assessment Statements - find out more
