You made it and filed your self-assessment return for 2018/19 by the 31 January 2020. However, having felt pleased with yourself, you realise to your horror that you have made a mistake and need to correct your return.
Can you do this and if so, how and by when?
Yes, you can
If you have made a mistake on your return, for example entered a number incorrectly or forgotten to include something, all is not lost. As long as you are within the time limit, the error can be corrected by filing an amended return.
If you are in time to file an amended return, the process that you need to follow will depend on whether you filed your return online or on paper.
If you filed your return online, you simply amend your return online. To do this:
Remember to check that it has been submitted and that you have received a submission receipt.
Check the revised tax calculation too in case you need to pay more tax as a result of the changes, but remember to take account of what you have already paid.
If you opted to file your return on paper by 31 October 2019, to make a change you will need to download a new tax return. This can be done from the Gov.uk website. Fill in the pages that you wish to change and write ‘Amendment’ on each page. Make sure you include your name and unique taxpayer reference (UTR) on each page too. Send the corrected pages to the address to which you sent your original return.
If you used commercial software to file the return, contact your software provider to find out how to file an amended return. If your software does not allow for this, contact HMRC.
You have until 31 January 2021 to make changes to your 2018/19 tax return.
If you have missed the deadline, you will need to write to HMRC instead. This may be the case if you find a mistake in your 2017/18 return after 31 January 2020. In the letter, you will need to say which tax year you are amending, why you think you have paid too much or too little tax and by how much. You have four years from the end of the tax year to claim a refund if you have overpaid.
Changes to the tax bill
If amending the return changes the amount that you owe, you should pay any excess straight away. Interest will be charged on tax paid late. If your 2018/19 liability changes, your payments on account for 2019/20 may change too.
If as a result of the changes made to the return you have paid too much tax, you can request a repayment from your personal tax account.
Partner note: See www.gov.uk/self-assessment-tax-returns/correction.