Emily Coltman

About the author: Emily Coltman, FCA is the chief accountant for FreeAgent, who make online accounting software for small businesses and freelancers.

How to amend a tax return that you've already filed

More information

Within a year after the filing deadline you can simply send an amended return and even after that you can write to HMRC and explain what needs to be changed and why. You can do this via your HMRC online account or, if you filed your original return through software such as FreeAgent, you need to use this software again to send the amended return.

For all Self Assessment tax return amendments after 12 months you need to write to HMRC to explain the changes you need made. The letter should be sent to:

Self Assessment
HM Revenue and Customs
United Kingdom

In the letter you should include:

  • the tax year the changes relate to
  • the reason why you think you’ve paid the wrong amount of tax
  • the amount you think you’ve overpaid or underpaid


Hi, I’m Emily Coltman, chief accountant to FreeAgent where we make online accounting software for small businesses.

What happens if you discover you’ve made a mistake on your tax return and you need to change it after you’ve filed it? The good news is that you can do that.

You’ve got a year from the tax return filing deadline to just simply send the revenue an amended version of your return.

How to amend an old tax return that you submitted over a year ago

If it’s more than that, for example, if you only realise a year and two months after the deadline that you need to make a change, you actually need to write to the Revenue and explain what needs to be changed.

We’ve put some more information under the video for you, so you know where to write to.

Did you know that you can file your tax return through FreeAgent? Click the link at the top of the page to find out more.

Thanks for watching and we’ll see you in the next clip.

Disclaimer: The content included in this guide is based on our understanding of tax law at the time of publication. It may be subject to change and may not be applicable to your circumstances, so should not be relied upon. You are responsible for complying with tax law and should seek independent advice if you require further information about the content included in this guide. If you don't have an accountant, take a look at our directory to find a FreeAgent Practice Partner based in your local area.