Who Needs to Register for Self Assessment? A Complete Checklist

Self Assessment is not only for the self-employed. HMRC requires a much wider group of people to register and file a return, and many only discover this after a deadline has already passed. If any of the situations below apply to you, registration is usually required.

Who must register

• You are self-employed as a sole trader and your gross trading income was over £1,000 in the tax year.
• You are a partner in a business partnership.
• You are a company director who received income not fully taxed through PAYE.
• You received rental income above the property allowance, whether from one property or several.
• Your income from savings or investments was untaxed and above the relevant threshold.
• You received dividend income above the dividend allowance.
• You need to pay the High Income Child Benefit Charge because you or your partner earned over the relevant threshold.
• You had income from outside the UK that is liable to UK tax.
• You disposed of an asset and need to report Capital Gains Tax that is not already covered by the real-time service.
• Your total taxable income was over £150,000 (or the current threshold for higher earners under PAYE only).

Situations people often miss

Two groups consistently get caught out. The first is landlords who assume small amounts of rental income do not count — HMRC's property allowance is only £1,000 a year, well below what many part-time landlords earn. The second is employees who claim Child Benefit while either partner's income creeps past the High Income Child Benefit Charge threshold; PAYE alone does not collect this charge, so Self Assessment registration is still required even though all your salary is already taxed at source.

The registration deadline

If this is the first time you need to file, you must register by 5 October following the end of the tax year the income relates to. For example, income first arising in the 2025/26 tax year (which ended 5 April 2026) must be registered by 5 October 2026. Miss this date and you can still register late, but you remain liable for the same filing and payment deadlines — registering late does not extend them.

What happens after you register

• HMRC issues a Unique Taxpayer Reference (UTR), which you need for every future return.
• You will usually need to set up a Government Gateway account if you do not already have one.
• Once registered, HMRC expects a return every year until you formally tell them your circumstances have changed.
• If your situation was temporary — for example a single one-off capital gain — you can ask HMRC to close your Self Assessment record once it is dealt with.