You should decide and set up your Ref # policy before setting up the system.
Ref #s are unique identifiers used on all Documents and Trading partners (Customers, Suppliers, and Workers). Once set and saved on any of the aforementioned they cannot be changed.
Users can import existing identifiers i.e. account number, or manually set the reference number.
Reference numbers can be set to auto-generate and increment from a fixed starting point. You can prefix reference numbers for meaningful distinction and recognition.
Every Document and Trading partner type has a ‘Ref # Generation‘ tab. The tab can be accessed from the ‘Configure’ action on the respective Document or Trading partner.