Self Assessment Deadline 31 January 2027: Your Step-by-Step Checklist
If you're self-employed, a landlord, or have income that isn't taxed at source, you probably need to file a Self Assessment tax return. Here's how to get the 2025/26 return done calmly – before the rush.
Key dates for the 2025/26 tax year
| Date | What happens |
| 5 October 2026 | Deadline to register for Self Assessment if this is your first year |
| 31 October 2026 | Paper return deadline |
| 30 December 2026 | File online by this date if you want tax under £3,000 collected through your PAYE tax code (where eligible) |
| 31 January 2027 | Online return deadline and deadline to pay any tax owed for 2025/26, plus your first payment on account for 2026/27 if one applies |
| 31 July 2027 | Second payment on account for 2026/27, if one applies |
The tax year 2025/26 ran from 6 April 2025 to 5 April 2026.
What happens if you're late
- Return 1 day late: £100 fixed penalty – even if you owe no tax.
- 3 months late: £10 a day, up to £900.
- 6 and 12 months late: further penalties of £300 or 5% of the tax due, whichever is higher.
- Late payment: interest, plus extra penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months.
Check the exact current rules on GOV.UK – search "Self Assessment penalties".
Your checklist
- Find your UTR (Unique Taxpayer Reference) and your Government Gateway login.
- Gather your income records: invoices, sales, rent received, P60 or P45 from any job, bank interest, dividends.
- Gather your expenses: receipts for allowable business costs – equipment, travel, phone, software, insurance, repairs on rental properties.
- Choose your expenses method: actual costs, or simplified expenses / the £1,000 trading allowance if they give a better result. You can't use both on the same income.
- Work out your figures – total income minus allowable expenses gives your profit.
- File online through your HMRC account and save a copy.
- Pay by 31 January – by bank transfer, debit card or a Budget Payment Plan.
Tips to save time and stress
- Start in November or December. HMRC's phone lines and your own nerves are both calmer.
- Keep records monthly next year. Ten minutes a month beats a weekend of searching through receipts in January.
- Making Tax Digital is coming. From April 2026, sole traders and landlords with qualifying income over £50,000 must keep digital records and send quarterly updates. The threshold drops to £30,000 from April 2027.
This guide is general information, not legal, tax or immigration advice. Always check the official GOV.UK guidance before you act.