Self Assessment deadlines for the 2025/26 tax return and what late penalties apply
Published · 4 min read · Figures checked . UK rules and rates change, so check the official sources below before you act.
Self Assessment tax returns for the 2025/26 tax year have fixed dates for filing and paying. This guide explains who has to send a return, the key deadlines up to 31 January 2027, payments on account and the penalties for being late.
Who this guide is for
This guide is general information for people in the UK who may need to send a Self Assessment tax return, such as sole traders and people with other untaxed income. It is not for people whose tax is fully taken through PAYE and who have no reason to send a return, and it is not advice for your own situation.
The dates below are for the 2025/26 tax year (6 April 2025 to 5 April 2026), whose return is filled in during 2026/27. They were checked on GOV.UK on 11 October 2026. Self Assessment works in the same way in England, Scotland, Wales and Northern Ireland, although Scotland has its own Income Tax rates and bands.
Who has to send a return
GOV.UK says you must send a return if any of these applied in the last tax year:
- You were a self-employed sole trader and earned more than £1,000 before deducting any tax-relief claims.
- You were a partner in a business partnership.
- You paid Capital Gains Tax when you sold or disposed of something that rose in value.
- You owed the High Income Child Benefit Charge and did not pay it through PAYE.
- You are an off-payroll worker repaying a student or postgraduate loan.
You may also need to send one if you have untaxed income, such as rental income, tips, savings interest, dividends or foreign income. HMRC can also ask you to send a return, and if it does, you must. GOV.UK points to a "check if you need to send a tax return" tool for people who are unsure.
What the dates mean
The 5 October date has now passed. GOV.UK says that if you register after it, HMRC will send a letter or email giving a return deadline three months from its date. You still need to pay by 11:59pm on 31 January 2027.
Paper returns must reach HMRC by 11:59pm on 31 October 2026. Online returns can be submitted until 11:59pm on 31 January 2027. Both could be sent from 6 April 2026.
If you would like HMRC to collect what you owe through your tax code, GOV.UK says the return must be in by 11:59pm on 30 December 2026. After that, the tax has to be paid another way.
Payments on account
Some people pay their bill in advance in two instalments, called payments on account. They are due by 31 January and 31 July. Each one is half of the tax you owed for the previous year, and they also cover Class 4 National Insurance for self-employed people.
GOV.UK says you do not have to make them if either of these is true:
- The tax you owed last year was under £1,000.
- Last year you paid more than 80% of your tax outside Self Assessment, for example through your tax code.
If your final bill is more than your payments on account, the difference is a balancing payment, due by 31 January. If you expect a lower bill, you can ask HMRC to reduce your payments on account, but you will be charged interest if the final bill turns out higher than you said.
Penalties for being late
GOV.UK sets out separate penalties for sending a return late and paying late.
- Late filing: an initial penalty of £100.
- After 3 months: extra daily penalties of £10 a day, up to a maximum of £900.
- After 6 months: a further penalty of 5% of the tax due or £300, whichever is greater.
- After 12 months: another 5% or £300, whichever is greater.
- Late payment: 5% of the tax unpaid at 30 days, again at 6 months and again at 12 months, plus interest on the amount owed.
Penalties should be paid within 30 days of the date on the notice. You can appeal if you have a reasonable excuse. GOV.UK also says there can be a penalty for registering late if you do not pay all your tax by 31 January.
Check before you act
Deadlines, penalties and rules can change, and your own position may differ. It is worth confirming everything on the official pages linked below before relying on this guide.
Sources
For information only. See our disclaimer and editorial standards. Spotted an error? Tell us.
