Photo: TeroVesalainen, Pixabay 

Everybody makes mistakes and it’s not the end of the world. But we can only imagine how annoying it is to realise that you've made a mistake in your Self-Assessment Tax Return. We know it takes a lot of effort and time to fill it in and leaving a mistake can be really frustrating.

But we also have some good news: on the contrary to the general belief, fixing mistakes in your SA tax return is not that hard! And we’ll tell you how to do that in this blog post.

How much time do you have to fix a mistake?

HMRC is quite generous with the terms given to make amendments or corrections and give you a full year to do that. For example, if you made a mistake in your tax return for the 2017-2018 tax year, you can still fix it by 31 January 2020.

And even if you missed this deadline, too, it’s not all lost: you can write to HMRC explaining your situation and reasons and appeal for the deadline to be extended. You should include information about the tax year for which you want to make amendments, the reasons why you think there is a mistake and the amount you think you’ve under or overpaid in your statement.

How to make amendments?

The steps you need to take to make amendments, depend on how you filed your tax return.

If you filled it online, follow these steps to make changes:

• Log in to your HMRC Self Assessment account
• Click on More Self Assessment details
• Click on At a glance
• Click on Tax return options
• Choose the tax return you want to make amendments to
• Make the needed changes
• File it again

If you sent a paper version, follow these steps:

• Download a new version of the return
• Make corrections to the pages where you made the mistakes
• Write the word ‘Amendment’ on each page that you’ve corrected
• Include your name and your Unique Taxpayer Reference on the corrected pages
• Send the pages with corrections to HMRC

If you paid too much tax

If your mistake resulted in you overpaying tax, you can try to reclaim it. You can claim a refund up to 4 years following the end of the relevant tax year.

If you are claiming a refund (it is also called overpayment relief), you need to inform HMRC that you are claiming for overpayment relief, provide proof that you’ve paid taxes for the relevant tax period and note that you haven’t tried to claim this refund before. Also, don’t forget to list how you would like to be repaid and provide your bank details.

If you didn’t pay enough tax

If you realised you haven’t paid enough tax and don’t want to get in trouble in the future, you can also make the needed amendments before it’s too late.

• Make amendments in your tax return
• The new figure should appear in your online SA account within three days
• You will see a new deadline for making the payment