Missed HMRC's 5 October sign-up? Register now, pay by 31 January
For sole traders and anyone else new to Self Assessment who did not tell HMRC by 5 October 2026: what happens now, and how to stay clear of a penalty.
What happens now that 5 October has passed?
Registering late is still possible, and still required. The deadline to tell HMRC you need a 2025 to 2026 tax return was 5 October 2026. The register page on gov.uk is blunt about it: "If you tell HMRC after 5 October 2026, you could get a penalty." You get a new filing date. Late registrants do not get the normal 31 January date for sending the return. HMRC's deadlines page says: "If you register after 5 October 2026 HMRC will send you a letter or email with a different deadline to send your tax return by". That deadline is 3 months from the date on the letter or email. The payment date does not move. Same page: "You must still pay the tax you owe by 11:59pm on 31 January 2027 or you'll get a penalty." The short version: you get more time to file, not more time to pay. Missing 5 October is fixable. Missing 31 January as well is what turns it into a penalty.
Who needs to register late (and who doesn't)?
You need to act if you must send a 2025 to 2026 return and have either never sent one, or were registered before but did not need to send one for 2024 to 2025. That is the test on gov.uk. In real life that is the hairdresser who went self-employed last year, the plumber who started on his own, the dog walker with a side business. gov.uk says a sole trader needs a return if they "earned more than £1,000 (before taking off anything you can claim tax relief on)". The same applies if you became a partner in a business partnership, or had untaxed income such as "tips and commission" or "money from renting out property or land" (who must send a tax return). If you registered years ago but sent no return last year, you may only need to reactivate your account. Not affected: anyone who sent a 2024 to 2025 return. You file as usual, online by 31 January 2027. Limited companies pay Corporation Tax, so this story is not about them. Not sure? HMRC's check tool gives you the answer.
What should you do this week?
Register today, then work to two dates: HMRC's filing date and 31 January 2027. Every week you wait only shortens the time you have to prepare.
- ✓Check whether you need a return with HMRC's check tool. Do it today.
- ✓Register or reactivate on the register page. Waiting for your Unique Taxpayer Reference (UTR)? The same page links a checker that shows when to expect HMRC's reply. gov.uk gives no fixed number of days, so start now.
- ✓Write down the date on HMRC's letter or email. Your return is due 3 months after it. Put that date in your calendar the day the letter arrives.
- ✓Pay everything by 11:59pm on 31 January 2027. Start putting money aside now. If a penalty does arrive and you have "a reasonable excuse", gov.uk says you can appeal (penalties).
Payment deadline for 2025 to 2026 tax, also for late registrants
Source: gov.uk, Self Assessment deadlines
Common questions
What happens if I register for Self Assessment after 5 October?
HMRC sends you a letter or email with your own filing deadline, 3 months from the date on it. That replaces the usual 31 January filing date for you. Your payment date stays the same: the tax for 2025 to 2026 must be paid by 11:59pm on 31 January 2027, according to gov.uk.
Will I get a penalty for registering late?
Not automatically. gov.uk says: "If you register after 5 October and do not pay all of your tax bill by 31 January, you may get a 'failure to notify' penalty." It is based on the amount still unpaid and arrives within 12 months after HMRC receives your return. Pay in full by 31 January and that condition does not apply.
Do I still have until 31 January to pay?
Yes, and no longer. The payment deadline is 11:59pm on 31 January 2027, also for late registrants. After that gov.uk lists late payment penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest. Filing your return late carries separate penalties, starting at £100.
How long does it take to get a UTR?
gov.uk does not give a fixed number of days. The register page links a tool where you can check when to expect a reply from HMRC. Because your filing deadline only starts with HMRC's letter, the sooner you register, the sooner your 3 months begin and the more time you have before 31 January.
Luca Bonura started selling online at 17 and funded his first business with 4:30am shifts in a bakery. He built his own product brand, watched it fail, and rebuilt as a freelance performance marketer for everyone from small shops to HelloFresh. Seeing how hard growth is even for people inside the industry, he founded Adlarion. He writes The Small Business Digest in plain English: the news he wished he'd had when starting out.
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