Guernsey Tax Identification Number: Format, Lookup, and Registration

Guernsey does not issue a dedicated tax identification number. For international reporting, an individual’s Guernsey TIN is their Social Insurance number; an entity’s TIN is either its registry number or a tax reference number issued by the Revenue Service, depending on how the entity was formed and where it is tax-resident.¹

What Guernsey Uses Instead of a TIN

For individuals, the functional equivalent of a TIN is the Social Insurance number. It is issued at birth for anyone born in the Bailiwick of Guernsey, and on arrival for people who move to the island. The format is two letters followed by six digits: GY followed by six numbers.¹

There is a second number that often gets confused with the first. When you register for income tax, the Revenue Service assigns a tax reference number (TRN). Registration will also generate a Social Insurance number if you don’t already hold one.² The TRN is what you use for direct correspondence with the Revenue Service: filing returns, checking coding notices, and similar. The Social Insurance number is what a bank or investment firm needs when it asks for your TIN under international reporting rules. Different jobs, different numbers.

TIN Formats for Companies, Partnerships, and Other Entities

Entities use a wider range of identifiers depending on structure and where they were formed. The OECD sets out the specific formats Guernsey uses:¹

Companies incorporated in Guernsey use the Company Registration Number issued by the Guernsey Registry. These are sequential numbers between one and six digits long.
Companies that are tax-resident in Guernsey but incorporated elsewhere use a tax reference number from the Revenue Service. The format is a single digit, a letter, then six digits, often followed by a letter suffix (for example, 1C 123456 / O).
Partnerships registered in Guernsey use the Partnership Registration Number from the Guernsey Registry.
Partnerships registered elsewhere but tax-resident in Guernsey use a tax reference number from the Revenue Service. The format is a single digit, two letters, then six digits, often with a letter suffix (for example, 1PP 123456 / F).
Foundations and charities use the registration number from their respective register.
Trusts are not issued a TIN or equivalent. A Guernsey-resident trust reports “NOTIN” when asked for a tax identification number.

The trust position matters if you administer or hold an interest in a Guernsey trust and a foreign financial institution insists on a number: there isn’t one, and “NOTIN” is the correct response.

Where to Find Your Number

Your Social Insurance number appears on the Social Security contribution or insurance card issued by the Revenue Service, on Revenue Service correspondence, and on pay slips from a Guernsey employer.¹ Your tax reference number sits on Revenue Service letters as well, usually labelled “Tax Reference” or “Reference Number.”

If you use MyGov, the online States of Guernsey portal, you’ll need to validate your tax reference number the first time you log in before the Revenue Service features become available. Once validated, you can view and submit personal tax returns from the same account. If the Revenue Service tile doesn’t appear after you log in, contact the Revenue Service directly to sort out the link.³

For entity numbers, a company’s registration number can be checked against the Guernsey Registry record. Tax reference numbers issued to entities appear on Revenue Service correspondence addressed to the company or partnership.

Getting a Number if You Don’t Have One

Anyone who moves to Guernsey or starts earning income on the island needs to register with the Revenue Service under the Income Tax (Guernsey) Law, 1975. Registration forms ask for standard identifying information: name, date of birth, residential address, employment details, and expected income. That information also feeds into your initial tax coding.

You can submit the completed form through MyGov, or return it in person to the customer counter at Edward T. Wheadon House, Le Truchot, St Peter Port, GY1 3WH.⁴ Online is the preferred route. Sole traders should create an individual MyGov account; anyone submitting a corporate return needs a separate MyGov organisation account.⁵ Paper forms are still available, and the Revenue Service runs periodic drop-in sessions at Edward T. Wheadon House for help completing online returns.⁶

Registering issues both a tax reference number and, if you don’t already have one, a Social Insurance number.² From that point on you hold the identifiers you’ll need for both local tax filings and international reporting requests.

When You’ll Be Asked for It

The most common reason you’ll be asked for a Guernsey TIN is a request from a financial institution acting under international information-sharing rules. Guernsey participates in both the Common Reporting Standard and FATCA through intergovernmental agreements, and Guernsey financial institutions are required to collect tax identification details and report account balances and investment income to the Revenue Service, which then shares that data with tax authorities in other jurisdictions.⁷⁸

When a Guernsey bank or investment firm asks for a TIN, give your Social Insurance number if you are an individual, or the applicable registration or reference number if the account holder is an entity.¹ Supplying the wrong number, or none at all when one is requested, can trigger enhanced due diligence procedures, account restrictions, and in extreme cases account closure. Getting the identifier right the first time avoids all of that.

1
OECD. Guernsey Tax Identification Numbers
2
States of Guernsey. Revenue Service Explained
3
States of Guernsey. Technical Help With Your Online Tax Return
4
States of Guernsey. Registering With the Revenue Service
5
States of Guernsey. MyGov Registration
6
States of Guernsey. 2024 Tax Returns Available to Complete Online
7
States of Guernsey. Intergovernmental Agreements (FATCA)
8
States of Guernsey. Common Reporting Standard (CRS)