The deadline for submitting your Self Assessment depends on how you file:
- Online tax returns must be submitted by midnight on 31 January following the end of the relevant tax year.
- If you want HMRC to collect the tax you owe through your tax code, the deadline is earlier: midnight on 30 December.
- Paper tax returns must be filed by 31 October.
You can find the full details on Self Assessment filing deadlines on the official HMRC page: https://www.gov.uk/self-assessment-tax-returns
Missing these dates can result in automatic fines, even if you don’t owe any tax.
Late Filing Penalties: How Much Will You Be Fined?
Failing to submit your Self Assessment by the deadline results in an immediate £100 fixed penalty. This applies even if there is no tax due.
If the return remains outstanding, additional charges apply:
- More than 3 months late (from the end of April):
A daily fine of £10 per day for up to 90 days, adding a maximum of £900 to your penalty (totaling £1,000). - 6 months late:
An extra penalty of £300 or 5% of the tax owed, whichever is higher. - 12 months late:
Another penalty of £300 or 5% of the tax due, again whichever amount is greater.
You can read the full breakdown of HMRC Self Assessment late filing penalties here:
👉 https://www.gov.uk/self-assessment-tax-returns/penalties
The longer the delay, the more expensive it becomes.
What If You Didn’t Need to File a Return?
If you’re registered for Self Assessment, HMRC expects a tax return from you every year. Even if your circumstances have changed and you no longer need to file, you must inform HMRC in advance. Failing to do so will still result in a penalty for non-submission.
Late Payment Penalties for Self Assessment
In addition to late filing fines, HMRC also charges penalties and interest if your tax payment is overdue.
| Time payment is overdue | Penalty applied |
|---|---|
| 30 days late | 5% of the unpaid tax, plus interest |
| 6 months late | An additional 5% of the outstanding amount, plus interest |
| 12 months late | A further 5% charge, plus interest |
These penalties are cumulative, meaning they stack over time.
Full details are available in the HMRC guidance on late payment penalties and interest: https://www.gov.uk/self-assessment-tax-returns/penalties
Payments on Account: What You Need to Know
Payments on account are advance payments toward your next tax bill. If your Self Assessment bill exceeds £1,000, HMRC usually requires you to make these payments.
They are based on the assumption that your income will remain the same or increase. Instead of paying everything in one go, you pay:
- 50% of your previous year’s tax bill by 31 January, and
- The remaining 50% by 31 July.
Missing either payment deadline can trigger penalties and interest, just like the main January tax payment.
What If You Can’t Pay Your Tax Bill?
If you’re struggling financially, HMRC may allow you to set up a Time to Pay arrangement. This is a formal payment plan that lets you spread your tax bill over manageable monthly instalments, provided you contact HMRC and meet their eligibility criteria.
Can You Appeal a Self Assessment Penalty?
In some cases, HMRC may cancel penalties if you can demonstrate a reasonable excuse. These are assessed on a case-by-case basis and typically include situations such as serious illness, bereavement near the deadline, or significant technical issues.
If you believe a penalty was wrongly issued, you can submit an appeal either online or by completing form SA370.
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Note: It must be noted that the information provided in all our blogs are solely for the awareness purposes and are designed with the intention to create an ease for the reader to understand the rules and their importance. However, it should never be considered as an ultimate replication of rules. RezEx Accountants (RezEx Ltd) does not own any responsibility for any unpleasant event that may arise due to misinterpretation of a specific part or whole of the information.
