For many of us, filing Self Assessment is an essential (although not necessarily fun) part of self-employment. Although we know it’s important, other things can sometimes get in the way, leading to a missed Self Assessment deadline. In this article, we explore late Self Assessment submission (all the way back to 2019–20). Read on to learn how to submit late returns today!
When is the annual Self Assessment deadline?
For most people, the Self Assessment deadline is midnight on 31 January. This is the main deadline for filing Self Assessment Income Tax returns (online) each year. For instance, 31 January 2025 is the deadline for those needing to file Self Assessment for the tax year 2023–24.
One exception to this is submitting a paper return by post (now very rare). Paper submissions for Self Assessment are due earlier (midnight on 31 October), presumably because they take longer to process and are much more prone to human error.
Payments on account
Of course, paying your Income Tax is not just about submitting a Self Assessment: you also have to pay whatever you owe to HMRC. In this regard, don’t forget to familiarise yourself with “payments on account” and prepare to meet your payment deadlines on time (usually in January and July).
What happens if you miss the Self Assessment deadline?
Self Assessment is usually due every January (specifically, midnight on 31 January). Ultimately, it is a legal requirement for you to submit an Income Tax Self Assessment, if applicable to you. Failing to meet the relevant deadline can result in a penalty, such as a fine (starting from £100).
Why is Self Assessment important, anyway?
Legality aside for a moment, it could also be argued that it is your moral and civic duty to pay Self Assessment on time. This is because HMRC provides an essential portion of the UK government’s annual revenue, helping to support public services via taxes. However, life is not always straightforward and deadlines are sometimes missed.
What to do if you miss a deadline?
First of all, don’t panic. While it’s not a fun situation to be in, you aren’t the first to be there – and you certainly won’t be the last. The most important thing is to submit your late return as soon as possible.
"Reasonable excuses"
HMRC recognises a range of reasonable excuses leading to a missed deadline. These reasons might include sudden hospitalisation or bereavement, or technical issues. (See HMRC for more details.)
If your reason for missing the ITSA deadline falls into HMRC’s category of “reasonable excuses”, then you likely don’t need to worry too much. HMRC has a dedicated appeals process for dealing with such scenarios. Check the HMRC website for details and to get the ball rolling.
Other scenarios
If your late submission is not regarded reasonable, or if you can’t demonstrate that you had a reasonable excuse, then you may be subject to a penalty fine. This is not necessarily automatic: you only need to pay a fine when asked to do so by HMRC. However, acknowledging that you need to submit your Self Assessment is a great step towards making amends, and it’s best to submit it as soon as you can.
How to submit a late Self Assessment
Understandably, HMRC doesn’t exactly want to encourage late submissions. As such, there isn't much provision for late returns on the HMRC website – particularly if your Self Assessment is a couple of years late (or more).
However, it is possible to submit returns dating even several years back using third-party commercial software. This is because HMRC-recognised MTD software providers such as AbraTax are able to support Self Assessment reaching back a number of years.
Follow three simple steps to get started:
- Log into your Self Assessment dashboard
- Locate “New Self Assessment” and click “GET STARTED”
- Select a tax year ranging back to 2019–20
In the unlikely event that you need to file Self Assessment for a tax year prior to 2019–20, get in contact and we might be able to help!
TL;DR
- If you miss the 31 January deadline, you may be liable for a fine
- Late tax return fines begin from £100 (and can increase over time)
- AbraTax now supports Self Assessment back to tax year 2019–20 (for free!)