GIIN format validator
A GIIN is a composite, not a random string: each block is constrained, and the blocks have to agree with each other. Paste a column and this checks all four against the IRS composition rules — then decodes each one back into category and jurisdiction.
IRS GIIN composition · four blocks · category and country decoding · duplicate detection · nothing stored
Check a list of GIINs
Runs in your browser · nothing uploadedOne GIIN per line, or separated by commas, semicolons or tabs — paste a column straight out of a spreadsheet. Case and spacing are normalised for you. No lookup is performed against the FFI List; the structure check runs entirely on your machine.
A GIIN that passes here can still fail at submission. The tax transparency module carries GIINs, TINs and self-certification outcomes through due diligence into validated FATCA and CRS filings — with a free tier to start.
Create free account →Nineteen characters, four blocks
The IRS publishes the composition. Each block has its own alphabet and length, the separators are fixed, and the third and fourth blocks constrain what the second is allowed to contain.
FATCA ID
Uppercase letters and digits, randomly generated. The letter O never appears anywhere in a GIIN, so that it cannot be confused with zero — which makes a stray O a reliable sign of a transcription error rather than an unusual code.
Financial institution type
Five characters. 00000 for a Lead FI or a Sponsoring Entity, 99999 for a Single entity, and for a Member the last five characters of its own FATCA ID — sequential from 00001, then A0000 onwards once the numbers run out.
Category code
Two uppercase letters, from a closed set: LE Lead, SL Single, ME Member, BR Branch, SP Sponsoring Entity. A branch shares the first thirteen characters of the GIIN of the institution it belongs to.
Country identifier
The ISO 3166-1 numeric code of the institution or branch — 250 for France, 196 for Cyprus, 826 for the United Kingdom. 999 is used for Other. It identifies where the entity registered, not where its customers are.
Rules reviewed 21 August 2026 · IRS GIIN composition information · ISO 3166-1 numeric · format XXXXXX.XXXXX.XX.XXX
What this validator does
It catches transcription errors and internal contradictions before they reach a filing. It is not a lookup against the FFI List, and the difference matters more here than it does for an LEI.
It doesCheck the composition
- Confirms nineteen characters in four blocks with periods at positions 7, 13 and 16.
- Applies the alphabet of each block, and flags the letter O anywhere in the code.
- Checks the category code against the five permitted values.
- Cross-checks the type block against the category — a Single that does not carry 99999, or a Lead or Sponsoring Entity that does not carry 00000, is contradictory.
- Resolves the ISO 3166-1 numeric code to a jurisdiction and flags codes that are not assigned.
- Flags duplicates, and matches each branch to its parent where both are in your list.
It does notLook anything up
- Query the IRS FFI List. No call is made from this page.
- Tell you whether a GIIN was issued, or whether the registration is current.
- Confirm the code belongs to the institution you think it does.
- Detect a single mistyped character. There is no check digit in a GIIN to catch it.
- Determine your FATCA classification, or whether you need a GIIN at all.
- Produce anything you can file. It is a check, not a return.
No check digit means no arithmetic safety net
An LEI or an IBAN will reject a single transposed character on its own. A GIIN will not — change one digit of the FATCA ID and the result is still perfectly well formed. Structure checking narrows the field; only the FFI List closes it. Treat a pass here as "worth looking up", never as "confirmed".
Nothing you paste here leaves your browser
The structure check runs entirely on your own machine. No code you paste is sent to REGREP, to the IRS, or to anyone else. Nothing is written to a log, saved to a database, or passed to any analytics tool.
That is deliberate. A list of GIINs is a list of the institutions you deal with, and it is not something we want to hold.
About GIINs
What is a GIIN?
A Global Intermediary Identification Number: a nineteen-character identifier issued by the IRS through the FATCA registration system to foreign financial institutions, branches, direct reporting NFFEs, sponsoring entities, sponsored entities and sponsored subsidiary branches. It is how a registered institution identifies itself to withholding agents and tax administrations for FATCA purposes.
Why is the letter O never used?
To remove the ambiguity between the letter O and the digit zero. Because a GIIN has no check digit, that ambiguity would otherwise be unresolvable: there would be no way to tell a mistyped code from a real one. The exclusion is absolute, so an O anywhere in a code you have been given is an error in transcription rather than an unusual GIIN.
Why does the tool flag a Single entity that does not carry 99999?
Because the composition rules tie the two blocks together. A Single entity carries 99999 in characters 8 to 12; a Lead FI and a Sponsoring Entity carry 00000; a Member carries the last five characters of its own FATCA ID. A code whose category and type block disagree is internally inconsistent, which usually means two codes have been spliced together in a spreadsheet.
How do I recognise a branch GIIN?
By the category code BR, and by its first thirteen characters, which match those of the institution the branch belongs to. Only the country identifier differs, because the branch is registered in a different jurisdiction. Where both a branch and its parent appear in your list, this tool pairs them.
Does a well-formed GIIN mean the institution is registered?
No, and this is the distinction that matters. Structure tells you the code could exist. Only the IRS FFI List tells you it does, that it is current, and that it belongs to the institution named on the documentation in front of you. The list is published monthly, so a code approved since the last publication will not yet appear on it.
Do you store the codes I paste?
No. Everything runs in your browser and is discarded when you close or reload the page. No lookup is performed, so the codes are not sent anywhere at all.
A valid identifier is the start of a filing, not the end.
Create a free account and take account data through due diligence, TIN and GIIN checks, and validation into submission-ready FATCA and CRS XML.
No card required · free tier on core modules · nothing stored from this tool