In the merchant registration form (e.g., via the B2B Suite or customer registration), Spanish NIE numbers are currently rejected as invalid VAT/Tax IDs. However, the NIE (Número de Identidad de Extranjero) is the official fiscal identification number for foreigners in Spain and is accepted by the Spanish tax authorities.

A valid NIE follows this format:
Starts with X, Y, or Z → 7 digits → ends with a letter
Example: Y5432178P

Currently, the validation logic does not accept such values, blocking legitimate registrations from Spain-based users.