Multi-currency Stripe payouts: why picking the wrong amount breaks affiliate commissions

When customers pay in one currency and merchants settle in another, Stripe records two separate amounts — the presentment amount charged to the customer and the settled amount received by the merchant. Most commission systems default to the invoice's amount_paid field, which reflects the customer's currency and can be misleading when the merchant's account settles in a different one. Developers must deliberately choose whether affiliate commissions are based on what the customer paid or what the merchant actually received, as each approach carries different risk exposure to exchange rate fluctuations. Refunds and disputes complicate matters further, since Stripe reconverts at the current rate rather than the original transaction rate, potentially creating reconciliation gaps over time. The recommended fix is to record both presentment and settlement figures — along with the exchange rate and balance transaction ID — at the time of each commission calculation, so no values ever need to be re-derived later.