UK Self Assessment Filing Complete Walkthrough 2026/27
UK Self Assessment for 2026/27: who must file, the 5 October 2027 registration deadline, payments on account, late filing penalties and MTD for Income Tax.
Do you need to file Self Assessment for 2026/27?
GOV.UK says you must send a tax return if, in the tax year, any of these applied:
- You were self-employed as a sole trader and earned more than £1,000 before expenses (the trading allowance)
- You were a partner in a business partnership
- You had to pay Capital Gains Tax on something you sold or gave away
- You had to pay the High Income Child Benefit Charge (adjusted net income above £60,000) and do not pay it through PAYE
- You are an off-payroll worker repaying a student or postgraduate loan
- HMRC sent you a notice to file
You may also need to file for untaxed income: rent, tips and commission, savings interest, dividends, foreign income, or any taxable UK income if you are not UK resident. Employed people with HICBC can now pay it through their tax code instead (per GOV.UK).
Key dates for the 2026/27 tax year
| Deadline | Action |
|---|---|
| 5 October 2027 | Tell HMRC you need to file, if you have not filed before or did not need to for 2025/26 |
| 31 October 2027 | Paper return deadline |
| 30 December 2027 | Online return, if you want a bill under £3,000 collected through your PAYE tax code |
| 31 January 2028 | Online return, balancing payment and 1st payment on account for 2027/28 |
| 31 July 2028 | 2nd payment on account for 2027/28 |
Dates per GOV.UK Self Assessment deadlines and paying through your tax code.
The 6-step filing process
- Register at gov.uk/register-for-self-assessment - HMRC sends a Unique Taxpayer Reference (UTR)
- Gather documents: P60, P45 from any job you left, P11D for Benefit in Kind (BIK), bank interest and dividend details, rental records, business records
- Sign in to your HMRC online account (or use compatible software)
- Complete the sections relevant to your income (employment, self-employment, property, capital gains, dividends, savings, foreign)
- Submit the return - HMRC calculates the tax owed
- Pay by 31 January, for example by online banking, debit card or Direct Debit
Payments on account - the cash-flow trap
Payments on account are two advance payments towards next year's bill, each usually half of the tax you owed for the year just reported. You do not make them if that bill was under £1,000 or more than 80% of your tax was collected at source (per GOV.UK). The first year is the one that hurts:
- 2026/27 tax bill: £5,000 - due 31 January 2028
- Plus 1st payment on account for 2027/28: £2,500 - same date
- Total due 31 January 2028: £7,500
- Plus 2nd payment on account for 2027/28: £2,500 - due 31 July 2028
MTD for Income Tax
Making Tax Digital for Income Tax is phased in by qualifying income (gross self-employment plus property income), per GOV.UK:
- From 6 April 2026: qualifying income over £50,000 in 2024/25
- From 6 April 2027: qualifying income over £30,000 in 2025/26
- From 6 April 2028: qualifying income over £20,000 in 2026/27
If you are in, you keep digital records, send quarterly updates through compatible software (due by the 7th of August, November, February and May) and submit your tax return for the year through that software. Budget 2025 said there will be no late submission penalties for quarterly updates in 2026/27, and that the new late submission and late payment penalty regime will apply to all Income Tax Self Assessment taxpayers not already joining MTD from 6 April 2027 (per Budget 2025). See our MTD penalty points guide.
Common Self Assessment mistakes
- Registering late: if you tell HMRC after 5 October and do not pay all the tax by 31 January, you may get a failure to notify penalty based on the tax still unpaid (per GOV.UK)
- Forgetting payments on account: the first year's January payment is the bill plus half again
- Paying late: penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest at Bank Rate plus 4 percentage points (7.75% from 9 January 2026)
- Not keeping records: GOV.UK says the self-employed must keep records for at least 5 years after the 31 January submission deadline
- Late filing penalties stack: on £5,000 of tax, £100 + £900 + £300 + £300 = £1,600 for a return 12 months late
Related pages
Frequently asked questions
Who has to file a UK Self Assessment tax return?
GOV.UK says you must send a return if, in the tax year, you were a sole trader earning more than £1,000 before expenses, a partner in a business partnership, had Capital Gains Tax to pay, had to pay the High Income Child Benefit Charge and do not pay it through PAYE, or HMRC asked you to. You may also need to file for untaxed income such as rent, tips and commission, savings interest, dividends or foreign income. GOV.UK has a checker at gov.uk/check-if-you-need-tax-return.
When are the Self Assessment deadlines for the 2026/27 tax year?
Tell HMRC you need to file by 5 October 2027 (if you have not filed before, or did not need to file for the previous year). Paper return: 31 October 2027. Online return: 31 January 2028, or 30 December 2027 if you want a bill under £3,000 collected through your tax code. Pay the balance and any first payment on account by 31 January 2028; the second payment on account is due by 31 July 2028.
How do payments on account work?
Payments on account are two advance payments towards next year's bill, each usually half of the tax you owed for the year just reported, due on 31 January and 31 July. You do not make them if last year's bill was under £1,000 or more than 80% of your tax was collected at source. In your first year, a £5,000 bill means £7,500 due on 31 January (the bill plus a £2,500 first payment on account) and £2,500 more on 31 July.
What if I can't pay my Self Assessment bill?
Contact HMRC or use the online service to ask for a payment plan. GOV.UK says HMRC checks the plan is affordable, there is no fixed time limit on how long it lasts, and you will usually be asked to pay around half of what you have left each month after essential spending. Interest still runs on the unpaid tax at Bank Rate plus 4 percentage points - 7.75% from 9 January 2026, per HMRC's published rates.
What is MTD for Income Tax?
Making Tax Digital for Income Tax requires sole traders and landlords to keep digital records and send quarterly updates through compatible software. Per GOV.UK it applies from 6 April 2026 if your qualifying income (self-employment plus property income) was over £50,000 in 2024/25, from 6 April 2027 if over £30,000 in 2025/26, and from 6 April 2028 if over £20,000 in 2026/27. You still send a tax return for the year through the software.
What expenses can I claim against self-employed income?
Costs incurred wholly and exclusively for the business. Simplified flat rates are optional: 55p a mile for the first 10,000 business miles in a car or van and 25p after that, and £10, £18 or £26 a month for working from home 25-50, 51-100 or 101+ hours a month (GOV.UK). See our allowable expenses guide.
What's the late filing penalty?
Per GOV.UK: £100 as soon as the return is late, then £10 a day after 3 months up to £900, then the greater of 5% of the tax due or £300 after 6 months, and again after 12 months. On £5,000 of tax a return 12 months late collects £1,600 in filing penalties, before late payment penalties and interest.
Can I file my own Self Assessment or do I need an accountant?
You can file yourself through your HMRC online account or compatible software, or appoint an accountant or other agent to deal with HMRC for you. Whoever prepares the return, you remain responsible for keeping records and for the figures being accurate.
How do I register for Self Assessment?
Use the Register for Self Assessment service on GOV.UK. HMRC then sends you a Unique Taxpayer Reference (UTR), and the service lets you check when to expect it. You must tell HMRC by 5 October 2027 if you need to file for 2026/27; registering late can lead to a failure to notify penalty if tax is still unpaid after 31 January 2028.