Missed the Self-Assessment Tax Deadline? Here’s What to Do Next in the UK
"Missed the Self-Assessment tax deadline? Don’t panic! This guide outlines what to do next, including how to submit your return, pay any tax owed, and appeal penalties if necessary. Plus, we offer tips to help you stay on track for next year’s deadline." This description provides a quick overview while highlighting the main steps and tips.
3 min read


Missing the Self-Assessment tax deadline can feel daunting, but don’t worry – it’s not the end of the world. While there may be penalties, acting swiftly and sensibly can help you minimize the impact and get back on track. In this guide, we’ll walk you through the steps to take if you've missed the deadline and how to avoid the same mistake in the future.
What Happens If You Miss the Deadline?
In the UK, the Self-Assessment tax return deadline for online submissions is 31 January. If you’ve missed it, here’s what you can expect:
An Automatic £100 Penalty: This applies even if you don’t owe any tax or have already paid your bill.
Additional Penalties: If your return is more than three months late, you could face further penalties that add up quickly.
Interest on Unpaid Tax: If you owe tax, HMRC will charge interest on the amount due until it’s paid in full.
While these consequences may seem stressful, the key is to act quickly and avoid further delays.
Step-by-Step: What to Do If You Miss the Deadline
1.Submit Your Tax Return ASAP
Submitting your tax return should be your top priority, even after the deadline. The longer you leave it, the higher the penalties.
Gather Your Documents: Make sure you have everything ready, such as P60s, P45s, invoices, and receipts.
Use HMRC’s Online Portal: Log in to your HMRC account and complete your Self-Assessment. If you’re not registered, do so right away.
Double-Check Your Figures: Ensure everything is accurate to avoid further issues with HMRC.
2.Pay Any Tax Owed
If you owe tax, pay as soon as possible to reduce interest charges. You can make payment via:
Bank Transfer: Use your bank to transfer the funds.
HMRC Online Account: Make a payment through your online portal.
Debit or Credit Card: Pay directly by card.
If you can’t pay the full amount, don’t panic. HMRC offers a Time to Pay Arrangement, which lets you spread your payments over time.
3.Check for Penalties and Appeal if Necessary
Once you’ve submitted your return, HMRC will notify you of any penalties. If you think the penalty is unfair (e.g., due to a reasonable excuse), you can appeal. Some valid reasons include:
Serious illness or hospitalisation
The death of a close relative
Issues with HMRC’s online services
Unforeseen disasters, like fires or floods
To appeal, write to HMRC and explain your situation with supporting evidence.
How to Avoid Missing the Deadline in the Future
If you’ve missed the deadline this time, it’s a good opportunity to improve your tax planning. Here are a few tips to help you stay on track next year:
1.Mark Key Dates in Your Calendar
31 October: Paper tax return deadline
31 January: Online tax return and payment deadline
31 July: Second payment on account deadline (if applicable)
Set reminders well in advance to avoid last-minute stress.
2.Keep Your Records Organised Keep a proper system for invoices, receipts, and other financial documents. This will make completing your tax return much easier.
3.Use Accounting Software Tools like Xero, QuickBooks, or FreeAgent help you track your income and expenses in real time, simplifying tax return preparation.
4.Work with a Professional Accountant An accountant can manage your Self-Assessment on your behalf, ensuring it’s submitted accurately and on time. They can also offer valuable advice on tax planning and deductions.
What If You’ve Never Filed a Tax Return Before?
If you’ve never filed a Self-Assessment but believe you should have, don’t panic. Contact HMRC to explain your situation and register for Self-Assessment as soon as possible. While you may still face penalties, being proactive can help reduce the impact.
Final Thoughts
Missing the Self-Assessment tax deadline can be stressful, but it’s not the end of the world. By acting quickly, submitting your return, and paying any tax owed, you can minimize penalties and get back on track.
If you’re finding it difficult to navigate the process or need help with your tax return, PCL is here to support you. Our team of experienced accountants can guide you through every step, ensuring compliance and providing you with peace of mind.
Don’t let a missed deadline derail your finances—contact us today for expert support!