The self assessment deadline can creep up faster than you think. One moment you are promising yourself you will file early, the next the deadline has passed and panic sets in. If this sounds familiar, take a breath. Missing the deadline is stressful, but it is not the end of the world. What matters most is what you do next.
Step One: File as Soon as Possible
The longer you delay, the more penalties and interest build up. Even if you cannot pay your full tax bill straight away, submitting the return quickly will stop further late filing penalties from being added.
Step Two: Understand the Penalties
For the 2025–26 tax year, HMRC applies penalties as follows:
£100 if your return is up to 3 months late
Daily penalties of £10 per day (up to £900) if more than 3 months late
£300 or 5% of the tax due (whichever is higher) if more than 6 months late
An additional £300 or 5% if more than 12 months late
On top of this, interest is charged on any unpaid tax.
Step Three: Pay What You Can
Even if you cannot pay the full bill, make a part payment. This reduces the amount of interest you owe. It also shows HMRC you are taking the debt seriously, which can help if you need to negotiate a payment plan later.
Step Four: Set Up a Payment Plan
HMRC allows many taxpayers to set up a “Time to Pay” arrangement. This lets you spread your tax bill over monthly instalments. You can usually do this online if you owe less than £30,000 and your return is up to date. For larger amounts or more complex cases, you will need to call HMRC directly.
Step Five: Learn for Next Year
Missing the deadline once is a wake up call. Make it easier next time by:
Keeping records updated throughout the year
Using accounting software to automate reminders and submissions
Setting up calendar alerts well ahead of the January and July deadlines
Considering an accountant who can keep you on track and reduce stress
Final Thoughts
Missing the self assessment deadline is a setback, but it is not the end of your business journey. The important thing is to act quickly, limit the penalties, and get back on track.
If you want to avoid the stress next year, now is the time to put better systems in place. Need help with your tax returns or staying ahead of deadlines? Contact us today and take the worry off your shoulders.
