Hi there, @SB8.

The exchange gain will be reflected if the customer's currency is different from the currency of the bank account that is used to receive the payment. The difference of the converted amount from the invoice and the payment is the equation for the exchange gain and loss.

This is how it looks like:

If you've use a third-party tool, I suggest contacting their customer support to verify the transaction.

I added this article for future reference about the Multicurrency works in QuickBooks.

I'll be here if you need anything else in QuickBooks. Please don't hesitate to click the Reply button below. Stay safe there!