Most often, the transaction is broken not at a separate stage, but on the agreement between the stages. The contract talks about FOB, and the shipment is DAP. The certificate of origin is issued for one consignment, and the customs declaration indicates another. The documents are individually correct, but do not agree with each other.
So we design a transaction based on its dependencies: what needs to be signed before shipment, what needs to be signed before the return is filed, what needs to be signed before payment is received. Each document is linked to a stage rather than existing separately.
This is especially important for categories with tariff preferences: an error in the document of origin can cost not only an additional fee, but also a loss of preference for a series of subsequent lots.