Paper tax returns are due 31 October 2025, and new registrants must notify HMRC by 5 October 2025. Act early to avoid penalties.

Firstly, the deadline for submitting paper self-assessment tax returns is 31 October 2025. If you miss this deadline a £100 late filing penalty will usually apply, even if no tax is due, or if any tax owed is paid in full by the final deadline of 31 January 2026.

Further penalties increase the longer the return remains outstanding. If your return is still not filed three months after the deadline, daily penalties of £10 per day (up to a maximum of £900) will be charged. If the delay extends to six months or more, further fixed or percentage-based penalties may apply, significantly increasing the cost of non-compliance.

We strongly recommend that anyone still submitting paper returns consider switching to the online filing system. Filing electronically not only simplifies the process but also gives you an extra three months, with the deadline for online returns falling on 31 January 2026.

The second key deadline is 5 October 2025. This is the date by which you must notify HMRC if you need to complete a self-assessment return for the 2024–25 tax year and have not previously been required to file one. Failing to register in time can lead to penalties for late notification, even if you file your return on time later.

Being aware of these October deadlines and taking timely action can help you avoid unnecessary stress and potential fines if you were unprepared.