Can You Amend A Tax Return After Filing?

The run-up to a Self Assessment tax return deadline can be stressful, which is why it pays to get it done as early as possible. But in some cases, you may have a brainwave after the submission date – suddenly, you may realise that part of the tax return isn’t correct.

Can a tax return be amended after filing? Don’t panic, because HMRC does indeed grant an amendment period for any oversights. Whether you think you’ve declared too little, or too much, we’re going to tell you how a mistake can be rectified.

When can you amend a tax return after filing?

Currently, HMRC allow another 12 months to adjust Self Assessment submissions for the previous tax year. In practice, it means that you have until the 31st January 2023 to make any changes to the form declared for 20/21. This is conditional on hitting the initial deadline i.e. you must send it off when the tax return is due in the first place.

If you missed the Self Assessment tax return deadline, or you want to amend a tax return from a previous tax year, you’ll have to write a letter to HMRC explaining what you want to do. For example, you would have to obtain written approval for any changes made to your 2017/18 tax return. HMRC needs to know:

• the tax year you’re correcting
• how much you’ve over/underpaid
• why you think this is the case

You can make amendments up to four years after the end of the tax year in question. If the changes entitle you to a refund, you’ll also have to include:

• that you’re claiming ‘overpayment relief’, and that you haven’t previously tried to claim this
• evidence that you paid your initial tax bill
• details on how you’d like to be reimbursed
• a signed declaration that the information you’ve given is correct and complete to the best of your knowledge

Amending your most recent Self Assessment

Assuming that you need to adjust your most recent Self Assessment, there are three ways to do so:

• For online tax returns, simply log into your HMRC account, select ‘Self Assessment account’ and click the ‘More Self Assessment details’ button. From there, go to the ‘At a glance’ menu, and scroll down to ‘Tax return options.’ Once chosen, you can pick the relevant tax year, look through the document and file it again.
• Paper tax returns are slightly more complicated. To amend them, you must obtain the latest tax return forms, complete them a second time, and note the word ‘amendment’ on each page.
• If you’ve used GoSimpleTax, you need to login to your account and make any necessary changes. Then click ‘validate your tax return’ and select ‘yes’ on the question ‘Are you submitting an amended tax return (for the tax year you want to amend) to HMRC?’. In the additional information box, you will need to provide a message to HMRC stating the reason for the amended tax return submission.

Once you’ve adjusted your Self Assessment tax return, HMRC should give you an updated bill within a couple of weeks. This will include either a new deadline for tax you owe, or instructions about your pay-out.

Of course, the risk of an inaccurate tax return is much lower when you have Self Assessment software to hand, so you won’t need to ask questions like: can a tax return be amended after filing? GoSimpleTax makes it easy to complete on time, in full, with enough evidence to bear scrutiny from HMRC.

You don’t need to be an expert to navigate tax – we’ve done the hard work for you. Get started with free trial today.

Blog content is for information purposes and over time may become outdated, although we do strive to keep it current. It's written to help you understand your Tax's and is not to be relied upon as professional accounting, tax and legal advice due to differences in everyone's circumstances. For additional help please contact our support team or HMRC.