Self Assessment Registration: does it apply to you?
Taxes Management Act 1970 & Income Tax (Trading and Other Income) Act 2005
When this applies
As a sole trader or in a partnership, you must register for Self Assessment with HMRC by 5 October following the end of the tax year you started trading in. Registering late risks a penalty even before your first return is due.
When it does not apply
Self Assessment registration applies to sole traders and partners. Your limited company registers for Corporation Tax instead, and you personally only need Self Assessment if you have other untaxed income (for example dividends above the allowance).
What is at stake
A late registration penalty applies if you miss the 5 October deadline, on top of the usual late filing and late payment penalties on the return itself once it is due. HMRC can also charge interest on any tax paid late as a result.
What to do
Register for Self Assessment with HMRC by 5 October following the end of the tax year you started trading in (the tax year runs 6 April to 5 April), at gov.uk/register-for-self-assessment. You will get a Unique Taxpayer Reference (UTR) and then file a tax return each year covering your business income.
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Check your business →Reviewed: 2026-09-13 · Source: official guidance