Missed your UK self-assessment deadline? Here's what it's costing you every day

If you're a UK freelancer who missed the 31 January 2026 deadline, this isn't a gentle reminder. This is maths.

As of 16 March, HMRC is charging £10 per day on top of the £100 initial penalty. That started 1 March. Every day you don't file costs another tenner.

The penalty timeline

• 1 Feb 2026: £100 automatic penalty (even if you owe nothing)
• 1 Mar 2026: Daily penalties begin — £10/day, up to 90 days
• Today (16 March): 16 days of daily penalties = £260 total
• 31 May 2026: Daily penalties cap at £900 = £1,000 total
• 1 Aug 2026: 6-month penalty — £300 or 5% of tax due
• 1 Feb 2027: 12-month penalty — another £300 or 5%

These are just filing penalties. Late payment incurs separate charges plus interest.

How to stop the bleeding

File your return. Today. That's it. Filing stops the daily penalties immediately.

Don't have exact figures? File with estimates. HMRC explicitly allows this — you can amend later. An estimated return filed today saves £300 vs a perfect one filed next month.

Steps:

1. Log into Government Gateway
2. Navigate to Self Assessment → Complete your tax return
3. Fill in income (check bank statements) and expenses (conservative estimate)
4. Submit. Save confirmation reference.
5. Can't pay? Call HMRC about Time to Pay (0300 200 3822) before they chase you

Can you appeal?

Yes, if you have a reasonable excuse: serious illness, bereavement, hospital stay, HMRC system outage.

Not reasonable: "I forgot", "I was busy", "I didn't have the money."

File first, appeal second. Filing stops penalties. You appeal existing ones separately.

Free tools

I built a self-assessment penalty calculator that shows exactly what you owe right now.

Also: reasonable excuse guide, Time to Pay guide, and a first-timer's walkthrough.

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The bottom line: every day you wait costs £10. File today. Sort the details tomorrow.