The 5 October 2026 notification date has passed. GOV.UK required people to tell HMRC by that date if they needed a tax return for 2025 to 2026 and had either never sent a return, or had registered before but did not need a return for 2024 to 2025. If that described you and you have not told HMRC yet, register or reactivate now. Waiting does not remove the need to file or pay.
What 5 October is, and is not
5 October is a tell HMRC / registration (or reactivation) date for people in those two situations. It is not the deadline for submitting the tax return or paying the bill.
- Online return and payment: 11:59pm on 31 January 2027
- Paper return: 11:59pm on 31 October 2026
People who already file Self Assessment every year are not suddenly given a new universal “re-register by 5 October” duty. Use GOV.UK’s “check how to register” flow if you are unsure which path applies, including reactivation if you skipped 2024 to 2025.
If you are registering after 5 October 2026
GOV.UK says you could get a penalty for telling HMRC late. After a late registration, HMRC will send a letter or email with a revised deadline to send your tax return (three months from the date on that letter or email). You must still pay any tax owed by 11:59pm on 31 January 2027 or you can get a payment penalty. Practical catch-up reading: late Self Assessment penalties.
Practical next steps
- Confirm you actually need a 2025 to 2026 return (GOV.UK’s “check if you need to send a tax return” tool).
- Use Check how to register for Self Assessment on GOV.UK, including reactivation where relevant.
- Gather records early so the January filing date is not a scramble (documents checklist).
- Diary 31 January 2027 for online filing and payment.
If you want an accountant to prepare the return once you are registered, TaxSimba’s Self Assessment service is accountant-led from your documents. We cannot register you with HMRC in place of the GOV.UK process, and we do not guarantee penalty cancellation. Re-check GOV.UK for the wording that applies to you.
Keep proof of the late registration action
Illustrative preparation example.
If you missed the notification date, record when you applied or reactivated and retain HMRC’s acknowledgement. Put any filing date in the actual notice beside the separate tax-payment date. Do not assume waiting for a reference pauses every obligation.
Check: Which deadline comes from the notice, and which payment still needs arranging?
| Check | Practical action |
|---|---|
| Do you actually need a 2025/26 return? | Use the official checker and identify the income or other reason before choosing a registration route. |
| New registration or reactivation? | Follow HMRC's route for your existing record rather than creating duplicate registrations. |
| What does HMRC's notice say? | Record the specific filing deadline and keep the payment deadline separately. |
Does everyone re-register every October?
No. The notification rule targets people who need a return and have not filed before, or need to reactivate after a year without a required return.
Should I wait until January if I missed October?
No. Tell HMRC promptly and prepare records now. Check any revised filing deadline and the tax payment date rather than assuming more time for both.
Download a checklist for this guide
- Record why a return is required.
- Check prior Self Assessment registration and filing history.
- Submit the correct registration or reactivation request.
- Retain HMRC's acknowledgement and filing date.
- Plan tax payment independently from filing.