TRN and TIN

Your Tax Registration Number (TRN) is the 15-digit number the Federal Tax Authority issues when you register for VAT. It belongs on your tax invoices and in your VAT returns.

Your Tax Identification Number (TIN) is the first 10 digits of that TRN. E-invoicing uses the TIN, prefixed with the scheme code 0235, as your Peppol participant identifier — the electronic address your invoices are routed to.

So both apply: the TRN for VAT compliance, the TIN for the exchange itself. You can check a TRN with the authority's TRN verification tool.

Official source: Federal Tax Authority