GST (Goods and Services Tax): made of different formats for each country, and can include letters and numbers. More info here.

LIC CN (Business license in China, also called Unified Social Credit Code): made of 18 digits. More info here.

VAT (Value-Added Tax identification number): every country in Europe has its own format, but it always contains the 2-letter country prefix (FR for France) followed by 7 to 11 digits. More info here and here.

SIREN: 9 digits (can be the same for multiple companies that are part of the same structure). More info here.

SIRET: 14 digits (made of a 9-digit SIREN + a 5-digit NIC). More info here.

DUNS (Data Universal Numbering System): standard business identifier made of 9 digits. More info here and here.

QST (Québec Sales Tax): 16 characters long, with the following format: characters 1–10 are numeric, characters 11 and 12 are the letters "TQ", and characters 13–16 are numeric (commonly "0001"). More info here.

UEN (Unique Entity Number for specific types of entities): the format depends on the year — you can check in the links below. More info here and here.

CRN (Company Registration Number): an 8-character code with either 8 digits or 2 letters + 6 digits. More info here.

EIN (Employer Identification Number): made of 9 digits with the following format "XX-XXXXXXX". More info here.