What is the Self Assessment deadline for 2025-26?

The online deadline for your 2025-26 tax return is 31 January 2027, and any tax owed is due the same day. Paper returns must reach HMRC by 31 October 2026.

The 2025-26 tax year ran from 6 April 2025 to 5 April 2026. This is the return that decides whether many tradespeople and landlords join Making Tax Digital (MTD) in April 2027, so it matters more than usual. The dates below follow GOV.UK as checked on 16 October 2026.

The 2025-26 dates

If you registered after 5 October 2026, HMRC sends you a different filing deadline, 3 months from the date on its letter or email. Payment is still due by 31 January 2027, and paying late after a late registration can bring a failure to notify penalty.

If you file late

Your 2025-26 return is under the old Self Assessment penalties. That is true even if you started MTD in April 2026; the new points system applies only from the year you join. The late filing penalties are:

• £100 as soon as the return is late, whether or not you owe tax
• after 3 months, £10 a day, up to £900
• after 6 months, 5% of the tax due or £300, whichever is greater
• after 12 months, another 5% or £300, whichever is greater

Late payment brings penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months. Interest runs on top from the day after the deadline. GOV.UK gives the late payment interest rate as 7.75% from 9 January 2026. If you have a reasonable excuse, you can appeal a penalty.

Why file early

Filing on 31 January and filing in October give HMRC the same information. Filing early gives you a few things:

• You know your bill. You get months to save rather than days.
• A CIS refund comes sooner. Over-deducted CIS is claimed back through your tax return. The sooner after 5 April you file, the sooner HMRC can repay you.
• You know your MTD date. If your 2025-26 self-employed and property income before costs was over £30,000, MTD starts for you on 6 April 2027.

What this means for you

Not sure you need to send a return at all? Our free tax return checker asks a few questions and tells you.

If you have not filed yet, the online deadline of 31 January 2027 is the one that matters. The paper deadline is two weeks away and most people file online. Work out your bill before Christmas, because January can mean paying for 2025-26 and making your first payment on account for 2026-27 at the same time.

If your 2025-26 bill was £1,000 or more and 80% or less of it was collected at source, payments on account apply. Our guide to payments on account explains how a first-year bill can come to 150% of the tax for the year.

From April 2027, GOV.UK says the new points-based penalties apply to everyone who files a personal Self Assessment return, so the £100 rule is on its way out.

Steps to file your 2025-26 return on time

1. Find your Unique Taxpayer Reference (UTR) and sign in to your HMRC online account, or your filing software.
2. Gather your 2025-26 figures: income, business costs, CIS statements, rent and any employment, savings or pension income.
3. Total your self-employed and property income before costs, and run the free MTD check to see if MTD starts for you in April 2027.
4. Complete and submit the return. Keep the submission reference.
5. Check your bill and whether payments on account apply.
6. Pay by 31 January 2027. If you cannot pay in full, contact HMRC before the deadline about a payment plan.

There is more for tradespeople in the trades section and for landlords in the landlord section.