Late Self Assessment: What to Do Right Now (Step-by-Step)
Quick Answer
If you've missed the deadline, the most important thing is to file as soon as possible. Penalties increase the longer you wait. File now, pay what you can, and contact HMRC if you can't pay in full. Don't ignore it—that makes everything worse.
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Don't Panic—Act
Being late isn't ideal, but it's recoverable. Thousands of people miss the deadline every year. What matters now is taking action.
The sooner you file and pay, the smaller the damage.
Step-by-Step Action Plan
Step 1: File Your Return Immediately
Even if it's late, filing stops the daily penalties from growing.
- Log into your HMRC online account
- Complete your Self Assessment as accurately as you can
- Submit it
Can't find your UTR? See our UTR recovery guide.
Never registered? You'll need to register first, which takes time. Do it now.
Step 2: Pay What You Can
Once you know what you owe:
- Pay as much as you can immediately
- Use the correct payment reference (your UTR + tax year)
- Payment methods: online banking, debit card, BACS
Even a partial payment reduces the amount interest and penalties apply to.
Step 3: Contact HMRC If You Can't Pay in Full
HMRC offers Time to Pay arrangements. You can:
- Call the Self Assessment helpline (0300 200 3310)
- Explain your situation honestly
- Propose a payment plan
They're often reasonable if you're proactive. Ignoring them is the worst option.
Step 4: Keep Records of Everything
- Screenshot your submission confirmation
- Note the date and time you filed
- Keep payment confirmation
This protects you if there's any dispute later.
Understanding Late Filing Penalties
Penalties stack up over time. Here's the general structure:
| How Late | What Happens |
|---|---|
| 1 day | £100 penalty (automatic) |
| 3 months | £10/day for up to 90 days (up to £900 more) |
| 6 months | Greater of £300 or 5% of tax due |
| 12 months | Greater of £300 or 5% of tax due (again) |
Example:
- Filed 4 months late with £3,000 tax due
- Penalty: £100 + (30 days × £10) + £300 = £700 minimum
The exact amounts can vary. Check HMRC for current penalty rates.
Understanding Late Payment Penalties
Separate from filing penalties, there are penalties for paying late:
| How Late | Penalty |
|---|---|
| 30 days | 5% of unpaid tax |
| 6 months | Another 5% |
| 12 months | Another 5% |
Plus interest on the outstanding amount from the due date.
Can You Appeal a Penalty?
Sometimes. HMRC may cancel penalties if you have a reasonable excuse.
Examples of reasonable excuses:
- Serious illness (you or close family)
- Bereavement
- Fire, flood, or theft affecting records
- Technical issues with HMRC systems
- Postal delays for paper returns
NOT reasonable excuses:
- "I forgot"
- "I was too busy"
- "I didn't know I had to file"
- "My accountant didn't remind me"
If you think you have grounds, appeal online or write to HMRC explaining your situation with evidence.
Worked Example: Filing 2 Months Late
Situation:
- Deadline: 31 January
- You file: 31 March (2 months late)
- Tax owed: £4,000
- You pay: 15 April (2.5 months late)
Penalties:
- Late filing (under 3 months): £100
- Late payment (30+ days): 5% × £4,000 = £200
- Total penalties: £300
Plus interest on the £4,000 from 31 January to 15 April.
If you'd waited 6 months, penalties would be much higher.
How to Prevent This Next Year
1. File early
The tax year ends 5 April. You can file from 6 April. Don't wait until January.
2. Set calendar reminders
- October: Start gathering records
- November: Begin your return
- December: Submit draft
- January: Final check and pay
3. Track income and expenses throughout the year
If records are ready, filing takes an hour, not a week. See our record keeping guide.
4. Set aside tax monthly
Having the money ready removes payment stress. See our tax set-aside guide.
5. Know your deadlines
Mark them. Respect them.
Common Mistakes
1. Waiting "until you have time"
Time doesn't magically appear. Every day costs more.
2. Ignoring HMRC letters
They don't go away. Interest and penalties grow.
3. Filing but not paying
Filing stops some penalties. But payment penalties apply separately.
4. Guessing figures to file quickly
Submit accurate information. Wrong figures cause problems later.
5. Not keeping payment proof
If HMRC can't match your payment, you'll need evidence.
FAQ
I'm only one day late—what happens?
£100 penalty, regardless of how much you owe.
I can't afford to pay. What do I do?
File anyway (to stop filing penalties), then call HMRC about Time to Pay.
Can I appeal the penalty?
Only if you have a reasonable excuse. "I forgot" doesn't count.
Will being late affect my credit score?
HMRC doesn't report to credit agencies directly, but unpaid debts can escalate to bailiffs eventually.
I filed but haven't paid. What now?
Pay as soon as possible. Interest is accruing. Call HMRC if you need a payment plan.
What if I never registered?
Register now. You'll face penalties for late registration too, but it's better than continued non-compliance.
Can HMRC take money from my bank?
In extreme cases, yes. They have enforcement powers. Don't let it get that far.
Does the penalty apply if I owe no tax?
Yes. The £100 penalty applies even if your tax bill is zero.
What's the deadline for online filing?
31 January after the tax year ends.
Is there any way to avoid all penalties?
Not if you're genuinely late. But acting quickly minimises them.
Next Steps
File now. Pay what you can. Contact HMRC if you need help. Then set up a system so it doesn't happen again.
Learn about setting aside tax, Payments on Account, and all the key deadlines.
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.