The Self Assessment deadline 2027 is 31 January for most online returns covering the 2025/26 tax year. If you are a sole trader, landlord or individual with income to declare, now is a good time to organise your paperwork and work out what you owe.
At Southside Accountants in Wimbledon, our advice is simple: prepare your return before the January rush. Here is a practical checklist to help you get started.
What does the Self Assessment deadline 2027 cover?
The return covers the tax year from 6 April 2025 to 5 April 2026. The usual online filing deadline and payment deadline are both 11:59pm on 31 January 2027. The standard paper filing deadline was 31 October 2026.
Check any specific deadline HMRC has given you. If you register after 5 October 2026, HMRC says your filing deadline will be three months from its letter or email, but the payment deadline remains 31 January 2027. See HMRC’s Self Assessment deadlines.
Check whether you need a tax return
Sole traders generally need to file if their gross trading income exceeded £1,000 before expenses. Rental income, dividends, savings interest and foreign income can also create a reporting requirement, depending on your circumstances.
Being a company director does not, by itself, automatically mean you must submit a personal return. Check your own income and circumstances using HMRC’s guidance on who must file. If HMRC has asked you to send a return, do not ignore the notice.
Gather your records before starting
HMRC requires records to support an accurate return. For sole traders, that includes business income and expenses, alongside personal income records. Start by collecting the documents relevant to you:
- Business income records, bank statements and expense receipts.
- Rental statements and supporting property expense documents.
- P60s or P45s, and details of taxable employment benefits.
- Dividend statements and details of taxable savings interest.
- Information about pension contributions and Gift Aid donations.
- Details of other income or disposals that may need reporting.
Our suggested approach is to create one folder for the tax year, then group documents by income source. Flag anything uncertain for review rather than guessing. HMRC explains the underlying requirements in its business records guidance.
Budget for payments on account
Your January payment can include the balance for 2025/26 plus an advance payment towards 2026/27. Payments on account are normally required unless your previous year’s relevant tax bill was below £1,000, or more than 80% of your tax was collected outside Self Assessment.
Each instalment is usually half the previous year’s relevant bill. For example, assume a £4,000 Income Tax bill, no earlier payments on account and no other adjustments:
- 2025/26 bill: £4,000.
- First 2026/27 payment on account: £4,000 × 50% = £2,000.
- Total due on 31 January 2027: £4,000 + £2,000 = £6,000.
- Second payment on account due on 31 July 2027: £2,000.
This is an illustration, not your personal calculation. Check your HMRC statement and the payments on account guidance.
Self Assessment deadline 2027: why start now?
Our recommendation is to use November to identify missing records and review your likely payment. Preparing early gives you time to ask questions and plan your cash flow.
Late filing normally starts with a £100 penalty. Further penalties can follow, while paying late can also lead to penalties and interest. Read HMRC’s penalty guidance.
Self Assessment help in Wimbledon
Need help preparing for the Self Assessment deadline 2027? Southside Accountants supports sole traders, landlords and individuals in Wimbledon SW19, Mitcham and surrounding South London areas.
Explore our tax return services or contact Southside Accountants to discuss your requirements.
Guidance checked on 1 November 2026. This article provides general information; the treatment of your income depends on your circumstances.