What is the cheapest way to do a tax return as a sole trader?

What is the cheapest way to do a tax return as a sole trader? The cheapest way is to file it yourself on HMRC's own online service, which HMRC's guidance calls free. Your 2025-26 return is due online by 11:59pm on 31 January 2027, and any tax is due the same day. HMRC's guidance for agents lists it as the "HMRC free online service". To use it you need to be registered for Self Assessment, your Unique Taxpayer Reference (UTR) and your sign-in details. GOV.UK says you must submit it online by 11:59pm on 31 January 2027, and pay any tax by the same time. A paper return must reach HMRC by 11:59pm on 31 October 2026. Yes. You report your pay before deductions and the total CIS deductions on your own Self Assessment return, and HMRC works out your tax. Over-deducted CIS is claimed back through your tax return. The sooner after 5 April you file, the sooner HMRC can repay you. Read the full answer, with every source, at rightotax.co.uk.