Self Assessment: Who Must File and Key Deadlines
For the 2025 to 2026 tax year (6 April 2025 to 5 April 2026), HMRC must receive an online Self Assessment return and any tax you owe by 11:59pm on 31 January 2027. Paper returns must reach HMRC by 11:59pm on 31 October 2026. If you have not sent a tax return before, you must tell HMRC by 5 October 2026.
More guides are in the tax hub.
Who has to send a tax return
According to GOV.UK, you must send a return if, in the last tax year, you were self-employed as a sole trader and earned more than £1,000 (before taking off anything you can claim tax relief on); you were a partner in a business partnership; you had to pay Capital Gains Tax; you had to pay the High Income Child Benefit Charge and do not pay it through PAYE; or you are an off-payroll worker repaying a student or postgraduate loan.
You may also need a return for untaxed income such as rent, tips, savings interest, dividends or foreign income. GOV.UK has a checker if you are unsure. Voluntary reasons include paying voluntary National Insurance contributions.
Registering by 5 October
You must tell HMRC by 5 October 2026 if you need a return for 2025 to 2026 and you have not sent a tax return before, by registering for Self Assessment. GOV.UK warns you could get a penalty if you tell HMRC after that date.
If you registered before, you may need to reactivate your Self Assessment account before filing.
Deadlines for the 2025 to 2026 tax year
You can send a return any time from 6 April 2026 onwards. Key dates for the 2025 to 2026 return:
| What | Deadline |
|---|---|
| Paper return | 11:59pm on 31 October 2026 |
| Online return | 11:59pm on 31 January 2027 |
| Pay through your tax code (online) | 11:59pm on 30 December 2026 |
| Pay tax owed | 11:59pm on 31 January 2027 |
To pay through your tax code, file online by 30 December if you meet GOV.UK’s conditions. Your tax code then collects the bill in equal instalments over 12 months. There is also a 31 July deadline if you make payments on account.
Payments on account
Payments on account are instalments towards your next tax bill, including Class 4 National Insurance if you are self-employed. There are two payments, each usually half of the tax you owed last year, due by midnight on 31 January and 31 July.
You do not have to make them if last year’s bill was under £1,000, or if you paid more than 80% of last year’s tax outside Self Assessment. A balancing payment is due by 31 January if instalments are too low. If you know your tax will be lower than last year, you can ask HMRC to reduce your payments on account; if you reduce them and your bill is higher than expected, you are charged interest on the difference.
Ways to pay
According to GOV.UK, you can pay by Direct Debit, online or telephone banking, debit or corporate credit card, at a bank or building society, or by cheque. A Budget Payment Plan spreads Direct Debit payments towards your next bill.
You can pay through PAYE when you owe less than £3,000, already pay tax through PAYE, and filed by the deadlines for code payment. A Time to Pay arrangement may be available if you cannot pay in full. Late payment brings interest and possible penalties.
Penalties for filing or paying late
Late filing brings an initial £100 penalty, then £10 per day (up to £900) after three months, and further 5% or £300 charges after six and twelve months. Late payment penalties are 5% of unpaid tax at 30 days, six months and twelve months, plus interest. You can appeal with a reasonable excuse. Registering after 5 October and missing the 31 January payment can bring a failure to notify penalty.
Correcting a return
You can correct a return within 12 months of the deadline, online or on paper. For the 2024 to 2025 tax year GOV.UK’s example deadline is 31 January 2027; online, wait 72 hours after filing before updating. After that, write to HMRC; overpayment relief is available up to four years after the tax year. Refunds may be set against tax due in the next 45 days. Tell HMRC promptly if you no longer need to file.
Making Tax Digital for Income Tax
From 6 April 2026, Making Tax Digital for Income Tax applies if self-employment and property income is over £50,000 (qualifying income is before expenses, from your previous return). You still file Self Assessment for the year before you start. Sign-up needs Self Assessment registration and a return filed in the last two years. From September 2026, GOV.UK says HMRC will sign up people who need it for 2026 to 2027 and have not joined themselves. No penalty points for late quarterly updates in 2026 to 2027; late return and payment penalties still apply.
Frequently asked questions
Do I need to send a tax return if I earn a little from a side business?
You must send a return if you were self-employed as a sole trader and earned more than £1,000 in the last tax year, before taking off anything you can claim tax relief on. GOV.UK has a checker if you are not sure whether you need to file.
What happens if I register after 5 October?
If you register after 5 October 2026, HMRC sends a letter or email with a different filing deadline, three months from the date on it. You must still pay any tax you owe by 11:59pm on 31 January 2027.
How much is the penalty for a late tax return?
The initial late filing penalty is £100. After three months, HMRC can charge £10 per day up to £900. Further penalties apply after six and twelve months, based on 5% of the tax due or £300, whichever is greater.
Do I have to make payments on account?
You do not have to make payments on account if the tax you owed last year was less than £1,000, or if you paid more than 80% of last year’s tax outside Self Assessment, for example through your tax code.
Can I pay my Self Assessment bill through my tax code?
You can pay through your PAYE tax code if you owe less than £3,000, already pay tax through PAYE, and submitted a paper return by 31 October or an online return by 30 December. The tax is then collected in equal instalments over 12 months.
Sources
Disclaimer: This article is general information and not personal financial, tax or legal advice. Check your own situation with HMRC, GOV.UK or a regulated adviser.