What is a UK self-employed registration number?
The difference between your Unique Taxpayer Reference, National Insurance number and self-employed registration.
Short answer: There is no single number called a ‘self-employed registration number’ for every situation. When you register for Self Assessment, HMRC issues a Unique Taxpayer Reference (UTR). Your National Insurance number is separate. A company, partnership or VAT registration can create further numbers, so use the one requested by the form or organisation you are dealing with.
Key points
- Your UTR identifies your Self Assessment record.
- Your National Insurance number is different.
- Company, partnership and VAT numbers are separate.
- Do not publish a UTR or send it to an unverified contact.
Registering as self-employed
Register with HMRC when you need to report self-employed income. HMRC then issues or confirms the UTR used for Self Assessment. Keep the registration letter and online account details with your tax records.
Which number should you use?
A tax return normally asks for the UTR, while payroll, identity and social-security processes may ask for the National Insurance number. Read the label carefully before entering either number.
If you work across borders
Living abroad does not by itself cancel a UK Self Assessment record. Review where the work was performed, the UK connection and any treaty or social-security issue before registering or filing.
Written and reviewed by Matthew S Manderson CTA ATT AMIT
Reviewed 3 September 2026. General guidance only; tax treatment depends on individual facts.