I have a business requirement to dissallow creation of duplicate accounts with the same VAT number, unless new submitted account form has a parent account id which has the same VAT Number.
Is this achievable with OOB functionality of deduplication rules (I guess not)?
What would be the most elegant way to deal with issue:
1. Custom realtime workflow performing the checkup and throwing error when record is created?
2. On field change javascript controlling the duplicate Vat number?