Deadlines
Missed the tax return deadline? Don't panic.
It's 1 February, the kettle's on, and you've just realised your tax return didn't go in. First, breathe. Thousands of people are in exactly the same spot, and if you act quickly it's usually far smaller than it feels.
The short answer
If your return goes in late, there's a £100 penalty, even if you owe no tax. That stays at £100 as long as you file within three months. Tax paid late also picks up interest, and an extra 5% if it's still unpaid after 30 days. So the best thing you can do is file and pay as soon as possible, and if you can't pay it all, set up a payment plan with HMRC.
What happens, and when
Penalties build up the longer things are left, so the timing matters more than anything. Here's how it works for the tax return due on 31 January 2027:
| How late | Late filing | Late paying |
|---|---|---|
| 1 day | £100 fixed penalty | Interest starts, day by day |
| 30 days | 5% of the tax still unpaid | |
| 3 months | £10 a day, for up to 90 days (up to £900) | |
| 6 months | £300, or 5% of the tax due if that's more | Another 5% of the tax still unpaid |
| 12 months | Another £300, or 5% if that's more | Another 5% of the tax still unpaid |
The good news is in the top two rows. If you file and pay within the first month, it's usually just the £100 and a little interest.
Leah's late return
Leah cleans holiday lets in Devon and made £16,000 profit last year. Her bill came to £892. A busy January and a poorly child meant she missed the deadline.
- She filed on 20 February. Penalty: £100.
- She paid the full £892 the same day. Interest: a few pounds.
- Because she paid within 30 days, there was no 5% penalty.
So it cost her just over £100. If she'd left it until the summer, it could easily have been more than £1,000. Acting quickly really is the whole trick.
What to do right now
- File it, even if it's not perfect. Use your best figures. If something changes later, you can amend the return for up to 12 months after the deadline.
- Pay what you can, today. Interest is only charged on what's still unpaid, so every bit helps.
- Can't pay it all? Set up a payment plan. HMRC calls it Time to Pay. If you owe £30,000 or less and your returns are up to date, you can usually set one up online in a few minutes and pay monthly.
- Open your post. HMRC will write with your penalty. Check it matches what you expected.
- Put the next date in your diary. If your bill is £1,000 or more, you will usually have an advance payment towards next year due on 31 July.
Excuses that work, and ones that don't
If something genuinely stopped you filing on time, you can appeal the penalty. HMRC calls this a "reasonable excuse". You need to appeal within 30 days of the penalty letter, and you still need to file as soon as you can.
Usually won't work
I didn't get a reminder.
The website was confusing.
I didn't have the money.
Someone else was meant to do it.
I forgot.
May well work
A serious illness or a stay in hospital.
A close family bereavement near the deadline.
A fire, flood or theft that destroyed your records.
HMRC's own online service was down.
A disability that made filing on time impossible.
If you're not sure whether your reason counts, ask us. We'll tell you honestly whether it's worth appealing.
"But I didn't even know I had to file"
If HMRC sent you a notice to file and you genuinely had nothing to report, you may be able to ask them to cancel the return, and the penalty with it. It's worth a phone call before you pay.
If you've been self-employed for a while and never registered, don't wait for HMRC to find you. Coming forward yourself almost always means smaller penalties. Our guide Do I need to register as self-employed? is a good place to start.
Next year, the easy way
- File early. You can file from 6 April. Doing it in spring means you know your bill months in advance.
- Save as you go. Our guide How much should I put aside for tax? shows how much to move into a tax pot each time you're paid.
- Let someone else remember. That's what we're here for.
This guide provides general information based on UK tax rules as at November 2026, for tax returns filed online. Penalties depend on your own circumstances, so specific situations may need professional advice.
Behind on your tax return?
We sort out late returns every year, without judgement. Get in touch and we'll get yours filed, check every penalty is right, and help you set up a plan if you need one.