Purchase Orders, Receipts, Invoices and Exchange Rates

Hi All,

Can someone tell me (or point me in the right direction of some documentation) on how PO’s, Receipts and invoicing works when dealing with different exchange rates.

Typically we would put on a PO at the exchange rate for the current month say 1.131 this is not locked on the Purchase order. When the goods are received the exchange rate on the system could have change to 1.21 and then when we receive the invoice the Supplier they could be using a different exchange rate again. We currently use FiFo costing for our raw materials…

TL;DR - What rate is used to calculate the FiFo costs…

Thanks,

John