Some users have permission to lock/unlock documents.
A Sales Order is complete when all the units sold have been added to Delivery Notes.
A Sales Order, NOT complete, is force closed by a user when the balance does no longer need to be processed.
A user can mark a Proforma as 'paid'.
A user can mark a Delivery Note as 'shipped'.
A user can mark an Invoice as 'paid'.
A user can mark a Return Authorisation as 'Received and Back to Stock' and define the quantities received and the quantities added back to stock.
