Hi Mark,
Under Administration - Approval Procedures, you can actually set up an approval for AR Invoices.
When an Invoice is raised, depending on the templates set up in here, the invoice might need to route for approval from other user.
When it is subjected to approval, the invoice raised will be created as a draft. Once it is approved, this draft will then be converted into document.
The same rules apply with invoices created from DI API when 'DI Approval' is enabled.
Regards
Edy