For 2025/26, the usual online Self Assessment filing and payment deadline is 31 January 2027. Paper returns are normally due on 31 October 2026. PAYE collection requests have an earlier online deadline, and a specific HMRC notice can change the filing date.
Key dates for the 2027 filing season
- 31 October 2026: paper tax return deadline (if you still file on paper).
- 30 December 2026: online deadline if you want HMRC to collect through your tax code where that option applies.
- 31 January 2027: online return and payment deadline for most people.
- 31 July: second payment on account deadline where payments on account apply.
If you need to tell HMRC you should be in Self Assessment for the first time (or again after a gap), GOV.UK also sets a 5 October registration-related deadline for the previous tax year. Check the deadlines page for the exact wording that applies to you, and see our 5 October registration guide.
What “deadline” covers
People often hear “31 January” and only think about clicking submit. In practice you usually need:
- the return filed online, and
- the balancing payment paid on time
Filing on time but paying late can still create charges. Payments on account, if they apply, are a separate rhythm. They are not a surprise “extra bill” invented by your accountant. See payments on account explained.
Example
Priya freelances and also has a small rental. She gathers records in autumn, uses TaxSimba’s accountant-led Self Assessment service to prepare the return, reviews it in December, and files well before 31 January 2027 instead of discovering missing invoices in the last week of January.
Common mistake
Waiting for a perfect final bank export on 30 January. If something is missing, you still need a plan: file on time with best available figures only where HMRC rules allow, or get advice quickly. Do not simply ghost the deadline.
If you later spot a genuine mistake on a return you already filed, that is usually an amendment problem, not a second “deadline” — act within HMRC’s correction window.
Getting ready
- Confirm which tax year you are filing for and diary 31 January 2027.
- Build a document checklist (income, expenses, property, dividends, and so on). See the documents checklist.
- Start early if your affairs are mixed or you may also have MTD obligations.
- Choose DIY software carefully, or use the Self Assessment accountant service if you want preparation handled.
Give filing and payment their own completion dates
Illustrative preparation example.
You approve a return on 20 January, but have no submission confirmation and have not arranged payment. Keep approval, filing and payment as three separate lines. Each needs its own evidence; marking the email approved does not finish the other two.
Check: Which of the three tasks is complete, and who is responsible for the remaining ones?
| Check | Practical action |
|---|---|
| Return filing | Check the tax year, route and applicable deadline. |
| Payment | Check the bill and allow time for the chosen payment method. |
| Special notice | Retain and read any HMRC deadline letter separately. |
Does filing early mean paying immediately?
Filing and payment dates are separate. Check the actual amount and due date rather than assuming the submission date creates a new deadline.
What if a supplier document is missing?
Identify the gap early and ask how HMRC's rules apply. Missing evidence is not a reason to invent figures or ignore the deadline.
Download a checklist for this guide
- Tax year and filing route
- Applicable HMRC notice
- Return preparation and approval status
- Tax and payments-on-account amounts
- Payment method and confirmation