When sending a payment instruction to the bank fixing the FX rate beforehand is an important requirement that we have seen. Corporates typically have a pre-negotiated rate. This could be against an FX Forward contract, have a spread agreed on Spot rates or would want to negotiate with the bank based on a view of instructions pending for a given date. Identifying the FX needs and signing a contract will be a treasury functions, SAP Treasury has comprehensive functions for this. What we have done for the Westpac adapter is we have enabled the following tags in the Pain.001 XML to capture the contract details. Westpac is reading these fields. For similar requirements please negotiate with your banks to get the contract details from the instructions.