Self Assessment 2025–26: Deadlines, Tax Return Dates and HMRC Guide

The 2025–26 UK tax year ran from 6 April 2025 to 5 April 2026. If you need to report income for that tax year, the main deadline for an online return and payment is 31 January 2027. The tax year and the year in which you file are different, which is why this guide refers to both 2025–26 and the 2026–27 filing period.

Self Assessment deadlines for 2025–26

If HMRC tells you that you need to register after 5 October, the registration deadline may instead be three months from the date of its letter or email. Check the date HMRC gives you rather than assuming every case follows the standard timetable.

Who needs to file a Self Assessment return?

Self Assessment is commonly used by people with untaxed income, including many sole traders, partners, landlords and people with certain investment or foreign income. You may also need to file for another reason set out by HMRC. The test depends on your circumstances and income, so use the official HMRC checker if you are unsure.

Registering with HMRC

Register online if you need to send a return and are not already set up for Self Assessment. Keep the information HMRC gives you, including your Unique Taxpayer Reference, because you will need it to file and pay. Registration is not the same as submitting the tax return.

Paper, online and tax-code filing

A paper return for 2025–26 must normally reach HMRC by 31 October 2026. Online returns have a later deadline of 31 January 2027. Some taxpayers can ask HMRC to collect a bill of up to £3,000 through their PAYE tax code, but the return must be filed online by 30 December 2026 and HMRC must be able to use that method. It is not available in every situation.

Paying Self Assessment tax

Any tax due for 2025–26 is normally payable by 31 January 2027. If HMRC requires payments on account, these are advance payments towards the following tax bill: the first is due by 31 January and the second by 31 July. The amount depends on the previous year’s liability and may not apply to everyone. Check your HMRC statement before making a payment.

Late returns and payments

Late filing and late payment can lead to penalties and interest. The consequences depend on how late the return or payment is and whether tax remains unpaid. If you have missed a deadline, file and pay as soon as possible and read HMRC’s official penalty guidance; do not wait for a reminder.

Useful checklist

• Confirm whether you need to file for 2025–26.
• Gather records of income, expenses, pension contributions and relevant tax already paid.
• Register by 5 October 2026 if the standard registration deadline applies.
• Choose paper or online filing and note the separate deadlines.
• Check whether payments on account apply to you.
• Keep evidence for the period HMRC requires.

Related UK tax guidance

If you are trying to understand the tax code used by your employer, see our UK tax code guide. For the legal deadlines, registration rules, payment options and special cases, use the GOV.UK Self Assessment deadlines guidance and HMRC’s Self Assessment overview.

Review date

Last reviewed: 2 September 2026. The deadline information in this article was checked against the GOV.UK guidance for Self Assessment tax returns. HMRC rules can change, so check the official page if your circumstances are unusual or you receive a different deadline from HMRC.