Self Assessment Deadlines Checklist (And What Happens If You're Late)
Quick Answer
The key dates to remember: register by 5 October after your first self-employed tax year, file online by 31 January, and pay your tax by 31 January. If you're subject to Payments on Account, there's also a 31 July payment. Miss a deadline, and penalties start immediately.
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The Self Assessment Yearly Rhythm
Here's the typical cycle for a UK tax year (6 April to 5 April):
If You're New to Self-Employment
| Milestone | Deadline |
|---|---|
| Start self-employment | Anytime |
| Register for Self Assessment | 5 October after the tax year ends |
| Receive your UTR | 10–20 working days after registering |
| Submit your first return | 31 January (online) |
| Pay your first tax bill | 31 January |
Example: You start self-employment in July 2024 (tax year 2024/25).
- Register by: 5 October 2025
- Submit return by: 31 January 2026
- Pay tax by: 31 January 2026
Ongoing (Each Year)
| Task | When |
|---|---|
| Tax year ends | 5 April |
| Gather records and prepare | April–October |
| Submit online return | By 31 January |
| Pay tax owed (balancing payment) | By 31 January |
| First Payment on Account | 31 January |
| Second Payment on Account | 31 July |
Key Deadline Details
Registration (5 October)
If you became self-employed for the first time in a tax year, you must register for Self Assessment by 5 October following the end of that tax year.
How to register: Use the GOV.UK website. You'll need your National Insurance number and some personal details. HMRC will send you a Unique Taxpayer Reference (UTR) by post.
Online Filing (31 January)
The deadline for submitting your Self Assessment tax return online is 31 January after the end of the tax year.
For tax year 2024/25 (6 April 2024 – 5 April 2025), the deadline is 31 January 2026.
Paper returns: If you file on paper (rare these days), the deadline is earlier—31 October.
Payment (31 January + 31 July)
Your tax payment is due by 31 January after the tax year ends.
If you're subject to Payments on Account, you'll also pay an instalment on 31 July.
What Happens If You're Late?
HMRC doesn't mess around with deadlines. Penalties can stack up quickly.
Late Filing Penalties
| How Late | Penalty |
|---|---|
| 1 day late | £100 (immediate) |
| 3 months late | £10/day for up to 90 days (up to £900 more) |
| 6 months late | £300 or 5% of tax due (whichever is higher) |
| 12 months late | Another £300 or 5% of tax due |
A return that's 12+ months late could cost you £1,600+ in penalties alone—before interest.
Late Payment Penalties
| How Late | Penalty |
|---|---|
| 30 days late | 5% of unpaid tax |
| 6 months late | Another 5% |
| 12 months late | Another 5% |
Plus, HMRC charges interest on unpaid tax from the due date.
Worked Example: The Cost of Being Late
Tom owes £4,000 in tax for 2024/25.
Scenario: He files and pays 4 months late (1 June 2026 instead of 31 January 2026).
| Penalty | Amount |
|---|---|
| Late filing (immediate) | £100 |
| Late filing (daily, 60 days × £10) | £600 |
| Late payment (5% of £4,000) | £200 |
| Total penalties | £900 |
Plus interest on the £4,000.
Moral: Even if you can't pay in full, file on time to avoid the filing penalties.
What to Do If You Miss a Deadline
1. File as soon as possible
The daily penalties (£10/day) stop once you file. Don't wait.
2. Pay what you can
Something is better than nothing. HMRC charges interest on the unpaid balance, but reducing it helps.
3. Contact HMRC
If you're struggling to pay, call HMRC and ask about a Time to Pay arrangement. They may let you spread payments over several months.
4. Check for reasonable excuse
Penalties may be cancelled if you have a genuine reason (serious illness, bereavement, fire, flood, etc.). "I forgot" or "I was busy" won't work.
5. Don't ignore it
Ignoring HMRC makes things worse. They can add more penalties, chase debts through bailiffs, or take money directly from your bank.
A Simple Record-Keeping Routine
Good records make filing easier and less stressful.
Monthly:
- Save/photograph all receipts
- Record income when it hits your account
- Transfer tax set-aside to a savings account
Quarterly:
- Review profit so far
- Check you're setting aside enough
- Catch up on any missed expenses
Annually (April–May):
- Gather all records for the year just ended
- Start preparing your return (don't wait until January)
Scam Awareness
HMRC scams are common. Protect yourself:
- Use GOV.UK only – don't click links in emails or texts claiming to be from HMRC
- HMRC won't ask for payment via gift cards or threaten immediate arrest
- Check suspicious emails by forwarding to phishing@hmrc.gov.uk
- Log in directly – type gov.uk into your browser, don't follow links
If you're unsure whether a message is genuine, call HMRC directly using the number on GOV.UK.
Common Mistakes
1. Registering too late
If you miss the 5 October deadline, you may face penalties. Register as soon as you start self-employment.
2. Waiting until January to start
Gathering a year's worth of records in a few weeks is stressful. Start earlier.
3. Not paying even when filing on time
Filing on time avoids filing penalties, but you'll still get payment penalties if you don't pay.
4. Ignoring Payments on Account
The July payment catches many people off guard. Learn how POA works.
5. Not keeping records for 5 years
HMRC can open an enquiry years later. Keep everything.
FAQ
Do I need to file if I made no profit?
Usually yes, if you're registered for Self Assessment. You can report zero profit. If you're no longer self-employed, you can ask HMRC to remove you from Self Assessment.
I missed the deadline—what now?
File immediately to stop daily penalties, pay what you can, and contact HMRC if you need a payment plan.
How do I find my UTR?
Check previous tax returns, HMRC letters, or log into your HMRC online account. You can also call HMRC.
Can I get an extension?
Extensions are rarely granted. COVID-era extensions are over. Assume the deadline is fixed.
What if I can't afford to pay?
Contact HMRC and ask about Time to Pay. They're often willing to set up a payment plan.
Do I still file if I'm employed and self-employed?
Yes, if your self-employment triggers the need for Self Assessment. Your PAYE income will be included in the calculation.
What happens if I pay late but file on time?
You'll avoid filing penalties but still face payment penalties (5% after 30 days, etc.).
Can I file before the tax year ends?
No. You can only file after 5 April, once the tax year is complete.
When is the paper deadline?
31 October (three months earlier than online). Most people file online now.
Is the 31 January deadline ever moved?
Rarely. HMRC has occasionally extended deadlines for major events (COVID, for example), but don't count on it.
Next Steps
Mark the deadlines in your calendar now—and give yourself reminders two weeks before each one.
Read our guides on Payments on Account and how much tax to set aside.
Back to the Learn hub.
This guide is for general information only. Tax rules change, and everyone's situation is different. Always check the latest HMRC guidance and consider speaking to a qualified accountant if you're unsure.