Self Assessment is how many individuals report Income Tax to HMRC: sole traders, landlords, and others with income that does not all sit in PAYE. The deadline people remember is January. The work starts months earlier.
This page is general information. Confirm your exact dates, payments on account and any penalties with your accountant and current GOV.UK Self Assessment deadlines.
Tax prep helps you assemble a labelled pack before the deadline scramble. Ask answers from your documents and cites the source. Alfred prepares. A qualified professional signs off regulated tax work. Ask Alfred™ does not submit your Self Assessment return.
The dates most people need
| What | Typical timing |
|---|---|
| UK tax year | 6 April to 5 April |
| Paper Self Assessment return | Usually earlier than online (commonly 31 October after the tax year) |
| Online Self Assessment return | Usually 31 January after the tax year ends |
| Balancing payment (and often payments on account) | Often due by the same 31 January date for many filers |
Example (illustrative only): for the tax year 6 April 2025 to 5 April 2026, many people filing online need the return in by 31 January 2027. Confirm your year and any special cases with your accountant.
Filing versus paying
Sending the return and paying what you owe are related but not identical jobs. You can file on time and still have a payment due. Payments on account (if they apply to you) can mean cash leaves the bank even when you feel "already taxed through PAYE". Put the January payment on your cash forecast early. See cash flow forecasting that includes tax.
Self Assessment is not corporation tax
Limited companies file a CT600 and usually pay corporation tax on a different timetable (often nine months and one day after the accounting period). Personal Self Assessment sits on the individual. If you are both a director and a sole trader or landlord, you may have both calendars. See corporation tax payment deadline UK.
How Making Tax Digital changes the rhythm
From April 2026, many sole traders and landlords in Self Assessment move onto Making Tax Digital for Income Tax: digital records and quarterly updates through the year, with the annual Self Assessment still finishing the tax picture.
MTD does not remove the need to diary January. It means less "box of receipts in December" and more keeping records current. If you are not yet in MTD, the classic Self Assessment deadline still matters.
A calm prep checklist
Confirm you need to file using GOV.UK guidance and your accountant (do not guess from one payslip).
Diary 31 January for the online return and likely balancing payment, plus any earlier paper deadline if you still file on paper.
Gather income and expense records months early: bank, invoices, property statements, side income.
Ask about payments on account so January cash is not a surprise.
If you are heading into MTD, read the MTD for Income Tax 2026 guide and set a quarterly habit now.
If you miss the deadline
Late filing and late payment can attract HMRC penalties and interest. File and pay as soon as you can, and speak to a qualified professional if you are stuck. Do not ignore HMRC letters. Alfred can help you organise documents earlier; your accountant handles the regulated filing judgement.
What to read next
- Making Tax Digital for Income Tax 2026
- Cash flow forecasting that includes tax
- What is a CT600 (if you also run a limited company)
- Corporation tax payment deadline UK
- Self Assessment in the glossary
- Tax prep
- Ask
This page is general information for UK individuals who may need to file Self Assessment. Deadlines, payments on account and penalties can change. Check GOV.UK and your accountant for your situation. Nothing here is regulated advice, and nothing regulated should be submitted or paid on your behalf without human approval from a qualified professional.