partial payments in foreign currency
Base currency is EUR
The invoice is in a foreign currency, e.g. $4500
Customer makes three payments of $1500
The payments are received using the "Pay" button and the EUR amounts are entered in the payment form. The form doesn't record the USD amounts that the customer knows they sent us. Our internal representation of the payments in EUR is not meaningful for the customer.
If the customer asks how much is outstanding after the first payment, we need to tell them $3000 but this is not visible because everything was converted to EUR.