UUID_Validation true validate the UUID field to mitigate human error !REGEX(Contributor_UUID__c, "^[0-9(a-f|A-F)]{8}-[0-9(a-f|A-F)]{4}-4[0-9(a-f|A-F)]{3}-[89ab][0-9(a-f|A-F)]{3}-[0-9(a-f|A-F)]{12}$") Contributor_UUID__c UUID format is wrong. Please check before save.