The UK does not issue a single number called a "tax identification number". When a form asks a UK-resident individual for a TIN, the answer is usually your National Insurance number. HMRC's guidance for banks reporting under the Common Reporting Standard says so directly. Some forms will also accept your Unique Taxpayer Reference (UTR), the 10-digit number HMRC issues when you register for Self Assessment. Companies are different: under the platform and cryptoasset reporting rules, a UK company's TIN is normally its company registration number. Below is which number to give, where to find it, and why you are being asked.
What is a TIN?
HMRC's international exchange of information manual describes a TIN as "a unique combination of letters and/or numbers used to identify an individual or entity for the purposes of administering the tax laws" of a country. The term comes from international reporting standards: the OECD Common Reporting Standard (CRS) for bank and investment accounts, the model rules for digital platforms, and the Cryptoasset Reporting Framework (CARF). Each standard asks financial institutions and platforms to collect every customer's TIN and the country that issued it, so tax authorities can match the data they exchange.
Many countries issue one number for all tax purposes. The UK uses several, so the right answer depends on who you are and which regime the form relates to.
Which UK number is your TIN?
| Taxpayer | Number usually given as the UK TIN |
|---|---|
| Individual | National Insurance number (some forms accept your UTR instead) |
| UK company | Company registration number (platform and cryptoasset rules) |
| Limited liability partnership | Company registration number |
| General partnership | Partnership UTR |
| Trust | Trust UTR |
| Charity | Company registration number, or charity reference number if it has none |
The entity entries come from HMRC's guidance for digital platform operators, which the cryptoasset guidance largely repeats. Its other points apply generally:
- A National Insurance number is for individuals only. HMRC says it is not an acceptable TIN for a company or other entity;
- A VAT number is not a substitute. HMRC's platform guidance says a VAT registration number is not an acceptable substitute for a National Insurance number or company registration number;
- Your TIN comes from your country of residence. If you live outside the UK, give the identifier your country of tax residence issues, not a UK number. People who are tax resident in more than one country may have to give more than one TIN.
If a form's notes say which UK reference they want, follow the notes. The categories above are HMRC's guidance for the reporting regimes. They are not a rule that overrides what a particular form asks for.
How to find your TIN number
National Insurance number. It appears on payslips, your P60 and letters about tax, pensions or benefits. You can also see it in the HMRC app, in your personal tax account, or in Apple or Google Wallet if you saved it there. The app and the personal tax account let you download a letter that confirms it. HMRC will not give you your National Insurance number over the phone or by webchat. If you have never had one, you have to apply.
UTR. You get a UTR when you register for Self Assessment or set up a limited company. It is 10 digits long and may be labelled simply "tax reference". Individuals can find it in their personal tax account, in the HMRC app, or on previous returns and HMRC letters such as notices to file or payment reminders. It usually arrives by post around 15 days after registration. A company can request its Corporation Tax UTR online, and HMRC posts it to the company's registered address. Partnership and trust UTRs appear on the returns and letters for that partnership or trust. A trust that needs a UTR gets one by registering on the Trust Registration Service.
Company registration number. This is the number Companies House gives a company or LLP when it is incorporated. It appears on the certificate of incorporation and the public register.
Why banks, platforms and exchanges ask for it
- Banks and investment platforms (CRS). Financial institutions collect a self-certification of tax residence and the TIN when you open an account. From 1 January 2026, HMRC guidance also requires them to make reasonable efforts to obtain a missing TIN for existing accounts whenever they update customer information under anti-money laundering checks. That is why many people are now being asked for it out of the blue;
- Selling on digital platforms. Since 1 January 2024, platforms that facilitate sales of goods, services and lettings have collected sellers' details, including the TIN (a National Insurance number for UK individuals), and reported them to HMRC each year. HMRC points out that being reported does not automatically mean you owe tax;
- Cryptoasset exchanges (CARF). UK cryptoasset service providers have collected data since 1 January 2026. For UK residents this includes a National Insurance number or UTR, and for UK companies a company registration number. The first reports, covering calendar year 2026, go to HMRC between 1 January and 31 May 2027.
A TIN request is a data-collection step, not a tax demand. It does mean HMRC will receive information about your account balances, platform income or crypto disposals, so your tax returns should already reflect them. Where they do not, it is far better to correct the position yourself than to wait for HMRC to match the data. Our guide to voluntary disclosure to HMRC explains how.
Common mistakes
- Giving a VAT number. A VAT number identifies a business for VAT and does not replace the TIN. To check one, see our UK VAT checker guide;
- Giving a National Insurance number for a company. Entities need an entity number;
- Using a UK number after leaving the UK. Once you are tax resident elsewhere, that country's TIN is the one that counts;
- Leaving the field blank. Institutions have to follow up on a missing TIN, so the request will keep coming back.
Acumon advises individuals and businesses on cross-border tax reporting through our international tax team. We also help clients put their returns in order before platform or crypto data reaches HMRC through our crypto tax service. If you are unsure which number a form wants, or whether reported data matches your returns, contact us before you submit it.