What should a money converter show a customer before they pay?

While researching money converter use cases, I keep coming back to a product decision that looks small until it creates a support question: which rate should a customer see?

A reference rate is useful for comparing prices. The amount that finally appears on a card statement, bank transfer, or cash withdrawal can include a different rate, spread, or fee. Historical conversions have a separate problem: the rate and the date need to be visible, and some sources only publish on business days.

For people who sell internationally, how do you present this?

Do you show the reference rate, the expected settlement amount, both, or simply a note asking customers to check their provider?

I’m less interested in the formula than in the wording and workflow. What has reduced confusion in quotes, invoices, travel bookings, or marketplace checkout? A real example of a mismatch would be more useful than a general preference.