Unique key for this purchase (max 400 characters). Retrying with the same key returns the original result instead of buying twice. Keys expire; do not reuse one for a new purchase. If omitted, every call buys a new label.
Assigns who is billed for duties and import taxes: the sender (DDP) or the recipient (DAP). Does not affect the quoted or charged rate — duties are billed separately after the shipment moves. Omit to leave the choice to your carrier configuration.
