How do I validate TRN for B2B customers in Magento?

The TRN (Tax Registration Number) is the FTA-issued 15-digit number that’s required on all UAE B2B tax invoices. Validating it at checkout matters because:

1. An invalid TRN means the FTA rejects your tax invoice — you can’t reclaim input VAT.
2. Without TRN you can’t apply reverse-charge B2B treatment.
3. Customers with valid TRN often expect zero-VAT invoicing on cross-emirate B2B.

We add a trn field to the Magento customer entity + checkout, and validate via:

• FTA TRN Verify API (real-time, returns business name + status)
• Format validation (15 digits, starts with 100)
• Auto-set tax class to “B2B with TRN” on validation success
• Auto-emit FTA-compliant tax invoice with TRN, supply date, AED line totals, VAT-line breakdown

Invoice-template integration with Microsoft Dynamics / Zoho Books / Xero UAE for accounting reconciliation.