Name each currency
The price displayed to a customer, the currency charged and the currency paid out to a merchant may differ. Label them explicitly. A dashboard that stores only an amount and a generic currency field can lose the conversion context needed to explain a transaction.
A benchmark is not a quote
The ECB publishes reference rates for information and discourages their use for transaction purposes. An actual payment conversion can involve another agreed rate, time and fee structure. Compare the applicable quote or contract with the executed transaction instead of assuming a daily benchmark was promised.
A numerical example
In a fictional quote, €100 converts to $110 before a separately stated $2 charge. The recipient receives $108 if that charge is deducted from the converted amount. A different deduction currency or timing changes the calculation, so write down the exact assumptions before comparing providers.
Explain differences cleanly
Retain original amount, converted amount, rate direction, timestamp, rounding and separately identified fees. Refunds may introduce a different conversion moment, depending on the arrangement. Explain the customer’s actual records without promising that two conversions on different dates will produce identical domestic-currency amounts.