Few UK tax terms cause as much confusion as “tax identification number.”
You’re asked for one when opening an overseas bank account, registering on an investment platform, completing international tax forms, or setting up a business — yet HMRC never issues a document officially labelled “UK Tax Identification Number.”
So what number are you actually supposed to provide?
That uncertainty is exactly why “tax identification number UK” is searched thousands of times each month. People aren’t trying to avoid tax — they’re trying to give the correct identifier without delays, rejected forms, or compliance issues.
This guide explains, clearly and practically:
- What a tax identification number means in the UK
- Which number applies to individuals, self-employed people, and companies
- Where to find it step by step
- Real-world examples used by HMRC, banks, and international organisations
- Common mistakes that cause problems
Updated for 2026, this is a user-focused explanation — not a copy of HMRC internal manuals.
What is a tax identification number in the UK? |
What Is a Tax Identification Number in the UK?
A tax identification number (TIN) is a unique reference used by tax authorities to identify someone for tax purposes.
The UK does not issue a single universal tax identification number.
Instead, the UK uses different identifiers depending on the person or entity and the tax context.
The UK Tax Identification System (At a Glance)
| Situation | What Counts as a UK TIN |
|---|---|
| Individual employee | National Insurance number |
| Self-employed / Self Assessment | Unique Taxpayer Reference (UTR) |
| Limited company | Company Registration Number (CRN) |
| VAT-registered business | VAT registration number |
| International tax forms | NI number or UTR (context-specific) |
This system works well inside the UK, but often confuses when international forms expect a single “TIN.”
Is a UK Tax Identification Number the Same as a National Insurance Number?
For most individuals, yes.
Your National Insurance number (NI number) functions as your tax identification number in the UK.
National Insurance Number Explained
Format: AB123456C
Issued automatically when you:
- Start working
- Claim benefits
- Apply directly via HMRC
Used for:
- Income tax
- National Insurance contributions
- State pension records
- PAYE employment
If a form asks for your UK TIN and you are an individual employee, your NI number is usually the correct answer.
UK Tax Identification Number for Self-Employed People
If you’re self-employed, you’ll often be asked for your Unique Taxpayer Reference (UTR).
What Is a UTR?
A 10-digit number
- Issued when you register for Self Assessment
Used for:
- Tax returns
- HMRC correspondence
- Accountant and compliance matters
Where to Find Your UTR
- HMRC Self Assessment letters
- Your HMRC online account
- Previous tax returns
A UTR does not replace your NI number in all situations — it’s used specifically for Self Assessment and HMRC filings.
Also Read: Business Tax Return 2026: UK & US Deadlines, Forms & Filing
What Is the UK Tax Identification Number for Companies?
Limited companies do not use National Insurance numbers or personal UTRs.
Company Registration Number (CRN)
A company’s main tax identifier is its Company Registration Number (CRN).
Issued by Companies House
Found on:
- Certificate of Incorporation
- Companies House public records
Used for:
- Corporation tax
- Banking and compliance checks
- International reporting
VAT Registration Number (If Applicable)
If registered for VAT, your VAT number may also be requested — but it does not replace the CRN as the company’s core identifier.
How to Find Your UK Tax Identification Number (Step-by-Step)
If You’re an Employee
- Check your payslip
- Look at your P60 or P45
- Log in to your HMRC Personal Tax Account
- Review official HMRC letters
Your NI number will appear on all of these.
If You’re Self-Employed
- Log into HMRC online services
- Check Self Assessment correspondence
- Review past tax returns
Your 10-digit UTR will be listed.
If You Run a Limited Company
- Search your business on Companies House
- Check the Certificate of Incorporation
- Review VAT documents (if registered)
Your CRN is the key identifier.
Real-World Examples (2026)
Example 1: Opening an Overseas Brokerage Account
Requested: Tax Identification Number (TIN)
Correct UK entry: National Insurance number
Example 2: FATCA or CRS Tax Residency Form
Requested: TIN
Correct UK entry:
- Individual: NI number
- Company: CRN
Example 3: Filing a UK Self-Assessment Return
Requested: Tax reference
Correct entry: Unique Taxpayer Reference (UTR)
Common Mistakes to Avoid
- ❌ Using a VAT number instead of a personal tax identifier
- ❌ Entering a company CRN for individual tax forms
- ❌ Leaving the TIN field blank on international forms
- ❌ Assuming the UK issues a single “TIN certificate.”
These errors often cause delays, rejected applications, or compliance flags.
Why the Confusion Still Exists (2026 Insight)
The UK relies on context-specific tax identifiers rather than a single national TIN.
While efficient domestically, this clashes with international systems that expect one number per taxpayer.
As of 2026, HMRC still confirms that:
- The UK does not issue a standalone Tax Identification Number
- Existing identifiers remain valid for international reporting
This approach is unlikely to change in the near future.
FAQs
Q. How do I find my UK tax identification number?
In the United Kingdom, most individuals use their National Insurance number as their tax identification number. You can find it on your payslip, P60 or P45, HMRC Personal Tax Account, or official HMRC letters.
Q. Is a tax identification number the same as a National Insurance number in the UK?
Yes, for individuals. The National Insurance number (NI number) acts as the UK tax identification number for income tax, National Insurance, and most international tax forms.
Q. Does everyone have a tax identification number in the UK?
The UK does not issue a single universal tax identification number. However, everyone with tax obligations has a tax identifier, such as an NI number, Unique Taxpayer Reference (UTR), or Company Registration Number (CRN), depending on their situation.
Q. What is the UK tax identification number for companies?
The United Kingdom’s limited companies use their Company Registration Number (CRN) as their tax identification number. It is issued by Companies House and appears on the Certificate of Incorporation and public company records.
Q. Is a UTR the same as a tax identification number in the UK?
A Unique Taxpayer Reference (UTR) is a tax identifier used specifically for Self Assessment and HMRC tax returns. It is not used in all situations where a general tax identification number is requested.
Q. What should I enter if a form asks for a TIN and I’m in the UK?
If you are an individual, enter your National Insurance number.
If you are a company, enter your Company Registration Number (CRN).
Only use a UTR if the form specifically relates to Self Assessment or HMRC filings.
Conclusion
The UK doesn’t use a single tax identification number — and that’s the source of most confusion.
Once you know which identifier applies to your situation, everything becomes straightforward:
- NI number for individuals
- UTR for Self Assessment
- CRN for companies
- VAT number, where applicable
If you searched for a tax identification number in the UK, the real answer isn’t one number — it’s understanding which number to use and when.
Related: How to Avoid Paying Tax on Rental Income UK 2026–2027
