Definition
A tax registration number (TRN) is the unique number a tax authority issues to a business registered for VAT, which must appear on its tax invoices.
TRN meaning in the UAE and Saudi Arabia
TRN is a regional term. In the UAE, the Federal Tax Authority (FTA) issues a 15-digit TRN that identifies the business for VAT; businesses registered for corporate tax also receive a corporate tax TRN. In Saudi Arabia, ZATCA issues a 15-digit VAT registration number. Other countries use their own names, such as VAT number, or GSTIN in India.
Buyers check the supplier’s number before claiming input VAT, so a missing or wrong number on a tax invoice can block recovery.
Example (fictional): a UAE supplier prints TRN 100000000000003 on every tax invoice.
A TRN isn’t a trade licence or commercial registration number, which come from licensing authorities rather than the tax authority.