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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 can usually sort it out. You can amend your tax return, within certain time limits. If HM Revenue & Customs (HMRC) accepts your new figures, you'll receive a repayment or be told how much extra tax to pay.
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If you think you paid too much tax because you made a mistake on your tax return, the first thing you must do is correct the return. There are time limits to do this. You can claim any refund due at the same time. You can find out more in the sections below.
If you don't complete a Self Assessment tax return, the tax form you'll need depends on your circumstances. For example you may need form R40 to reclaim tax on savings and investments or form P50 to claim tax back if you've stopped working. In this case follow the link below to find out more.
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 or amend it. For example, if you send your 2013-14 online tax return by 31 January 2015, you have until 31 January 2016 to amendment it.
You can only amend your return after this date if you received your return late (after 31 July). In this case the letter telling you to complete a return will tell you when the deadline is for sending the return back. You have 12 months from this deadline to amend your return. For example if you received your 2013-14 return on 1 December 2014, the deadline for returning it is 1 March 2015 (3 months later). You have another 12 months, until 1 March 2016, to amend it.
If you owe more tax or have to pay a penalty as a result of the mistake, HMRC will tell you how much you need to pay and when and how to pay it. If you're think you're due a refund you can tell HMRC how you'd like to receive it.
If you sent your tax return online by 31 January, it's easy to amend it online too. You just need to log into your Self Assessment online account, go to the 'at a glance' page and choose the option to amend your tax return.
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' at the top of the front page.
You'll find the address to send it to on your tax return, tax calculation or Self Assessment Statement.
You might only realise you've made a mistake when it's too late to amend your return - see the time limits above. However you can still write to HMRC and tell them about the mistake. If you want to claim a refund you must tell HMRC within 4 years of the end of the tax year you're claiming for.
For example if you paid too much tax in the 2010-11 tax year, which ends on 5 April 2011, you must make a claim for a refund by 5 April 2015. If you don't make a claim within the time limit you'll miss out on any repayment due.
You must make any repayment claim in writing and it should include:
If you owe more tax or have to pay a penalty as a result of the mistake, HMRC will tell you how much you need to pay and when and how to pay it.
You should state on your tax return or letter how you would like the repayment to be made. You can have it deducted from any tax due on your next Self Assessment Statement, or you can ask for it to be sent:
HMRC aims to issue any repayment within 2 weeks, but it may take longer because of measures to protect you against fraud. Please allow up to 4 weeks for online requests or 6 weeks for post requests before contacting HMRC.
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.