Hola Gonçalo,
This problems is solved with the Setting “VAT Reg. Numer Masks” (in Systems module) where you can define different VAT Reg. Number formats for each country. Then you will have to link it to the Contact Card.
This is the Hansamanual on how to use the setting:
https://www.hansamanuals.com/main/english/mailnumber___4092/theconf___602/manuals/levelzero___4092/version___71/hwconvindex.htm
Kind Regards,
Juan Maddocks