Tax Identification Numbers (TINs) – what you need to know

If you’ve recently been asked for a “Tax Identification Number” (TIN number) by an overseas client, bank, or platform – and can’t find one on any UK tax document – there’s a good reason for that.  

The UK doesn’t issue Tax Identification Numbers (TINs) the way the US, EU member states, and many other jurisdictions do. Instead, HMRC and Companies House use separate sets of identifiers that, depending on the context, do the same job. 

Read on to learn what a TIN is, why the UK does things differently, and which UK identifier to provide when an overseas counterparty asks for your TIN. 

What is a Tax Identification Number (TIN)?

In short, a TIN is a unique combination of letters and numbers that a tax authority uses to identify an individual or entity for tax purposes.  

Most countries issue some form of TIN. For example, the US uses the Social Security Number (SSN) for individuals and the Employer Identification Number (EIN) for businesses, while EU member states issue their own equivalents.

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The TIN allows the tax authority to track who’s paying what, and increasingly, to share that information with other countries’ tax authorities under international reporting standards. 

The term itself isn’t widely used in the UK. HMRC and Companies House each issue their own reference numbers for specific purposes, but none of them is officially called a “TIN”.  

Does the UK have a Tax Identification Number?

No, the UK doesn’t issue a single, all-purpose number officially called a TIN.  

For international tax reporting, the UK’s functional equivalents are the Unique Taxpayer Reference (UTR) and the National Insurance number.

HMRC’s guidance on the OECD’s Common Reporting Standard confirms this: “For most individuals in the UK, the TIN will be their National Insurance number.” 

That doesn’t mean that overseas counterparties will accept “the UK doesn’t issue TINs” as an answer. They usually want a specific identifier they can record on their files, and your answer mainly depends on whether you’re being asked as an individual or on behalf of a business, and the reason for the request. 

So what do you use instead of a TIN?

The likely answer is one of these UK identifiers: 

• Unique Taxpayer Reference (UTR) – the closest TIN equivalent for limited companies and self-employed people; usually the right answer for tax-reporting requests. 
• National Insurance number – the recognised TIN equivalent for individuals. 
• Company Registration Number (CRN) – useful for company verification or vendor onboarding, but not a tax identifier in its own right. 
• VAT registration number – sometimes requested by overseas suppliers or marketplaces, particularly where VAT is involved. 
• Employer Reference Number (ERN) – rarely needed cross-border; mainly an internal HMRC PAYE reference.

We’ll cover each in detail below.

Why you might be asked for a TIN number

Three scenarios drive most cross-border TIN requests in the UK: 

• The OECD’s Common Reporting Standard (CRS) – an international framework under which tax authorities exchange information about financial accounts. If you open a bank or investment account overseas (or hold one in the UK as a non-resident), the institution is required to report your tax residency and TIN number to its local tax authority. The OECD publishes country-specific guidance on which identifiers each member jurisdiction recognises. 
• The US Foreign Account Tax Compliance Act (FATCA) – a similar regime that targets US persons holding accounts outside the US. It also requires non-US financial institutions to gather TIN-equivalent information. 
• The IRS’s W-8BEN form and W-8BEN-E form – completed by non-US individuals and entities receiving payments from US sources, to claim treaty benefits and avoid the default 30% US withholding tax. Both forms may ask for a foreign TIN, particularly when used to claim treaty benefits or to document a financial account. 

Company Registration Number (CRN)

The Company Registration Number (CRN), also known as the company number, is a unique 8-character string assigned automatically by Companies House when a company is registered. 

The CRN is the company’s public registration identifier, not a tax identifier. It may be useful for vendor onboarding or company verification, but where a foreign form asks for a tax identification number, a UK limited company will usually provide its company UTR instead. 

Despite the name, the CRN doesn’t always consist of just numbers – the format depends on the company type and the jurisdiction of registration.  

Where to find your CRN

You can find your CRN in several places: 

• Your Quality Company Formations Client Portal, by logging in and selecting “My Companies” – the number sits next to “Number” 
• The public Companies House register, by searching for the company name 
• The Certificate of Incorporation issued when the company was registered 

Unique Taxpayer Reference (UTR)

The Unique Taxpayer Reference (UTR) – also known simply as the tax reference – is a 10-digit number issued by HMRC. It usually appears in this format: 12345 67890. 

There are two distinct types of UTR: 

• Company UTR – issued automatically by HMRC by letter when a limited company is incorporated. The letter is usually received at the company’s registered office within around 14 days of incorporation. Once generated, the UTR appears on all future HMRC correspondence about Corporation Tax. 
• Personal UTR – issued to individuals who register for Self Assessment, including company directors with non-PAYE income to declare. A personal UTR isn’t issued automatically just because someone becomes a director; you have to register for Self Assessment to get one. 

The distinction matters when a foreign institution asks “the director” for their TIN. If the request relates to the individual (for example, a director opening a personal investment account abroad), you’d typically provide the personal UTR or NI number.  

If it relates to the company (for example, a US client onboarding the company), you should provide the company’s UTR. 

Where to find your UTR

The company UTR appears on every piece of HMRC correspondence about Corporation Tax – the original welcome letter, any reminders, payment statements, and the “Notice to deliver a Company Tax Return“.  

Personal UTRs will be listed on Self Assessment paperwork and inside the individual’s HMRC personal tax account. 

If a UTR has gone astray, HMRC can send a copy by letter to the registered office. You’ll need the CRN and registered company name to make the request.

National Insurance number

Most UK residents are sent a National Insurance (NI) number shortly before their 16th birthday. The number ensures that tax and National Insurance contributions are recorded against the correct individual. It follows the format AB123456D (two letters, six numbers, and a final letter). 

For company directors, the NI number becomes relevant when paying yourself through Pay As You Earn (PAYE).  

For most UK individuals, it’s also the recognised TIN equivalent for cross-border reporting under the Common Reporting Standard, and is the number HMRC’s internal guidance specifically points to. 

Where to find your NI number

You’ll find your NI number on payslips, your P60, HMRC letters, and inside your HMRC personal tax account online. If you can’t locate any of these, you can complete form CA5403 or call HMRC’s NI helpline on 0300 200 3500. 

VAT registration number

If you register for VAT, HMRC issues a unique 9-digit VAT registration number. VAT registration becomes mandatory once your taxable turnover exceeds £90,000 in any rolling 12-month period, but you can also register voluntarily below that level. 

UK VAT numbers are nine digits long and are commonly shown with the GB prefix – for example, GB123456789. Northern Ireland businesses that trade in goods with the EU may need to use the XI prefix instead – for example, XI123456789 – on documentation with EU customers or suppliers. 

VAT registration numbers must be shown on VAT invoices. Customers and counterparties often need them to verify VAT status. The VAT number usually arrives within 10 working days of HMRC accepting your application. 

Where to find your VAT number

You’ll find your VAT number on your VAT registration certificate, your HMRC online VAT account, and any VAT invoices you’ve already issued.  

If you’ve lost track of it and can’t find your initial registration documents, contact HMRC directly as they can re-send it to you.

What to send when asked for a TIN number

It depends on who’s asking and why. The table below illustrates the most common scenarios in which you may be asked for a TIN and what to consider sending. 

Who’s asking	Likely reason	What to send
US client/withholding agent (W-8BEN-E)	UK limited company claiming foreign status or treaty benefits	Company UTR as the foreign TIN, where required
US client/withholding agent (W-8BEN)	UK individual or sole trader	NI number or personal UTR, depending on the form
Overseas bank or investment platform	CRS/FATCA account opening	NI number for individuals; UTR for entities where issued
Foreign supplier or marketplace	Vendor onboarding/company verification	CRN, plus VAT registration number if VAT-registered

Keeping your TINs safe

Some of the identifiers above are intended to be public, while others should be kept to yourself unless you have a specific, trusted reason to use them. 

Public: 

• Company Registration Number – legally required on business letters, order forms, and websites. 
• VAT registration number – required on VAT invoices, and routinely shared so counterparties can verify VAT status. 

Private: 

• Unique Taxpayer Reference (company and personal) – HMRC reference; sharing this with those you don’t fully trust makes you a target for fraud. 
• Employer Reference Number – internal PAYE reference. 
• National Insurance number – personal identifier; share this only with HMRC, employers, banks, and other clearly legitimate requesters. 

If you’re asked for any private identifier and you’re unsure who’s asking or why, don’t send anything until you’ve verified the requester. HMRC won’t ask for a UTR by email or text out of the blue.

Are you a Quality Company Formations customer with an address service?

If you’ve taken our Registered Office Address Service or Director’s Service Address, we accept mail from official government bodies, including HMRC and Companies House, on your behalf. Mail is securely opened, scanned, and emailed to you – with copies stored in your Online Client Portal. 

That means if you’ve misplaced any of the identifiers listed above, the originating letter is likely in your Online Client Portal. To check, log in, select “My Mail”, and click on the relevant PDF. 

Ready to form your company?

A new UK limited company is automatically issued the most important identifiers – the CRN by Companies House on incorporation, and the company UTR by HMRC shortly afterwards.  

The ERN and VAT number follow when you register as an employer or hit the VAT threshold. 

If you haven’t formed your company yet, Quality Company Formations registers UK limited companies, with packages from basic registration to a fully inclusive service that includes a registered office, business address, and full compliance support.