Missed the 5 October deadline to register for Self Assessment? What to do now
21 October 2026 · 4 min read · Checked against GOV.UK 21 October 2026
Who needed to register
You need to register for Self Assessment if, in the tax year to 5 April 2026, you made more than £1,000 from working for yourself: a trade, freelancing, online selling or a side hustle. That's income before costs. Our trading allowance guide explains the £1,000 rule.
Will I be fined?
Not just for being late. HMRC can charge a "failure to notify" penalty, but it's worked out as a percentage of the tax that wasn't paid on time because you didn't register. If you register, file and pay by 31 January, there may be no unpaid tax and so nothing to charge.
Even if tax is paid late, the penalty is much lower when the mistake wasn't deliberate and you tell HMRC before they contact you. Within 12 months, it can be reduced to nothing.
What to do now
- Register online today on GOV.UK, choosing the option for self-employed people. You'll need your National Insurance number and a Government Gateway account (you can make one as you go).
- Wait for your UTR, a 10-digit Unique Taxpayer Reference. It comes by post, usually within 10 to 15 working days, and you may see it sooner in the HMRC app.
- Activate Self Assessment with the code HMRC posts you separately. It expires after 28 days, so use it when it arrives.
- Get your figures together: everything you were paid and the costs of the work, from 6 April 2025 to 5 April 2026.
- File online and pay by 31 January 2027.
Why January matters more
Missing 31 January has fixed penalties, whatever the reason:
- £100 if your return is even a day late, even if there's no tax to pay;
- £10 a day after 3 months, up to £900;
- 5% of unpaid tax at 30 days, 6 months and 12 months, plus interest.
If you've left registering until December or January, call HMRC once you've registered online if your UTR hasn't arrived. Post is slowest in the weeks before the deadline.
Getting ready for the bill
Your first bill can be bigger than expected, because it may include a payment towards next year too. Our guide to your first tax bill explains why, and the tax calculator works out your figure. HMRC's registration page is on GOV.UK (opens in a new tab).