Self Assessment Online: How to Complete and Submit Your Return as a Sole Trader
If you are a sole trader in the UK, you usually need to complete a Self Assessment tax return to report your income and pay any Income Tax due. This is because tax is not automatically deducted from your business profits as it is from wages or pensions. Here is a practical guide to help you complete and submit your Self Assessment return online.
Registering for Self Assessment
If you have not sent a tax return before or you started trading recently, you must tell HM Revenue and Customs (HMRC) by 5 October following the end of the tax year you are reporting on. For example, for the tax year ending 5 April 2026, you must register by 5 October 2026.
You register by signing up for Self Assessment through the HMRC website. If you register after 5 October 2026, HMRC will send you a letter or email with a different deadline to file your return, usually three months from the date of that communication. However, you still need to pay any tax you owe by 31 January following the tax year to avoid penalties.
Keeping Records
Before filling in your return, you need to have accurate records of your income and expenses. This includes invoices, receipts, bank statements, and details of any other income or allowable expenses related to your business. Keeping good records helps you complete your return correctly and avoid mistakes.
Filling in the Online Return
Once registered, you can fill in your Self Assessment return online from 6 April after the tax year ends. The return includes sections on your business income and expenses, as well as other income such as savings or dividends if applicable.
If you do not know your exact profit for the tax year when you start filling in your return, you should still submit it by the deadline. You can update or amend it later if needed.
Deadlines for Submission and Payment
- Online return submission deadline: 31 January following the end of the tax year (for example, 31 January 2027 for the 2025–26 tax year).
- Paper return deadline: 31 October following the end of the tax year (for example, 31 October 2026 for the 2025–26 tax year).
- Payment deadline: Tax owed must be paid by 31 January following the tax year. There is also a second payment deadline on 31 July for ‘payments on account’ if applicable.
Filing or paying late may result in penalties and interest charges.
Paying Your Tax Bill
HMRC calculates what you owe based on your return. You can pay your tax bill online, by bank transfer, or by other accepted methods. If you want your tax to be collected through your tax code (for example, by reducing your PAYE tax if you have a job), you must submit your return by 30 December following the tax year.
If you miss this date, you will need to pay your bill by other means.
Exceptions and Additional Notes
- Some people may be asked by HMRC to complete a return even if they do not think they owe tax.
- If you are unsure about your deadlines or how to register, check directly with HMRC.
- Partnerships and certain companies have different deadlines and filing methods.
In summary, the key steps are to register on time, keep clear records, complete the online return after the tax year ends, submit it by 31 January, and pay any tax due by the same date to avoid penalties.
Official reference: https://www.gov.uk/self-assessment-tax-returns. Topic-specific official guidance. Always check the latest official guidance. Related forms: Browse our form category.
Important: This article provides general information. Government rules, forms and procedures can change, and this article may not reflect the latest updates. Check current GOV.UK guidance or the relevant authority before relying on it. ITG & Co. is independent and is not affiliated with a government department.