A UK tax identification number is not one universal ID. The identifier requested depends on whether the person or organization is dealing with Self Assessment, National Insurance, company registration, Corporation Tax, or VAT. Sending the wrong number can delay onboarding and expose sensitive data.
UK identifiers compared
| Identifier | Used for | Issued by |
|---|---|---|
| Unique Taxpayer Reference (UTR) | Tax records such as Self Assessment or Corporation Tax | HM Revenue & Customs (HMRC) |
| National Insurance number (NINO) | National Insurance and individual interactions with tax and benefits systems | UK government |
| Company registration number (CRN) | Identifies a registered company on the public register | Companies House |
| VAT registration number | Identifies a VAT-registered person or business | HMRC |
A CRN is not a company UTR, and a VAT number is not proof that every invoice treatment is correct. HMRC’s international information manual explains that the UK does not issue TINs in the strict sense used by some countries; UTRs and NINOs are commonly treated as functional equivalents for individuals.
Where to find each number
- UTR: HMRC correspondence, the relevant online tax account, or tax-return documents.
- NINO: the person’s National Insurance record, certain government correspondence, or approved digital services.
- CRN: certificate of incorporation and the Companies House register.
- VAT number: VAT registration certificate and the business’s official VAT account.
Formats can vary by identifier and jurisdiction within the UK. Validate the field against the official document instead of inferring identity from length alone.
Which number should a form receive?
Ask the requester what legal and tax purpose the field serves. A cross-border tax form may ask for a residence-country taxpayer identifier; a customer verifying a company may need the CRN; a VAT invoice may require the VAT registration number. If instructions are ambiguous, obtain clarification in writing.
How to obtain or recover an identifier
Use official GOV.UK or HMRC channels. Company formation produces a CRN. Tax registration and activation processes generate the appropriate HMRC references. VAT registration is a separate process with eligibility and compulsory-registration rules. Recovery procedures differ, so do not apply for a duplicate simply because a reference is temporarily missing.
Protect tax identifiers
- Confirm the requester and legal basis before sharing a non-public identifier.
- Use a secure portal rather than ordinary email when possible.
- Limit access and log disclosures.
- Redact identifiers from general documents and screenshots.
- Do not treat a CRN found on a public register as proof that the sender controls the company.
Businesses operating in multiple jurisdictions can use the broader business registration number guide to distinguish legal registration from tax accounts.
Frequently asked questions
Is a UTR the same as a National Insurance number?
No. They are separate identifiers with different purposes and should not be substituted.
Is a Companies House number a tax number?
No. The CRN identifies the registered company; HMRC issues separate tax references.
Does every UK business have a VAT number?
No. A VAT number is issued after VAT registration, which may be compulsory or voluntary depending on current rules and circumstances.
Sources reviewed
Last reviewed: August 15, 2026. This is general information, not UK tax or legal advice. Verify current requirements with GOV.UK or a qualified adviser.