Is dynamic currency conversion against Mastercard rules?

No, DCC is permitted, but only with the cardholder's active choice. The violation occurs when conversion is applied by default, the choice screen is misleading, or the disclosure of rate and margin is inadequate. Documented cardholder election is your entire defense, so store it.

The customer is only upset about the exchange rate. Can they charge back the whole purchase?

Under this condition the issuer generally files for the currency difference when the underlying purchase is not disputed. If the full amount was charged back on a pure conversion complaint, challenge the scope in your second presentment along with the evidence of currency choice.

Mastercard · Processing Errors

Reason code 4846: Correct Transaction Currency Code Not Provided

This claim arises when the currency in clearing did not match the currency of the transaction, most often around dynamic currency conversion done without the cardholder's informed choice. Originally its own code, 4846 was consolidated into 4834 (Point-of-Interaction Error) and now travels as a currency-related dispute condition. Cardholders typically notice it as an unexpected conversion or a worse exchange rate than anticipated.

Issuer filing window

typically 90 days from the central site business date, filed under the 4834 umbrella

Merchant response window

typically 45 days to respond via second presentment

Why 4846 chargebacks happen

DCC was applied at checkout or the terminal without giving the cardholder a genuine choice to pay in their card's currency.
The transaction currency transmitted in clearing differed from the currency displayed and agreed to at the point of sale.
A cross-border gateway configuration defaulted all cardholders to merchant currency conversion regardless of their selection.
Currency codes were mismapped during a gateway or PSP migration, so settlements cleared in the wrong currency entirely.

How to fight a 4846 chargeback

Produce the checkout or terminal screen flow showing the cardholder was offered both currencies and actively chose the one that cleared.
Provide the receipt displaying the transaction currency, converted amount, and exchange rate disclosure the cardholder accepted.
Show the clearing record matches the currency agreed at checkout, which defeats a claim that the wrong code was transmitted.
If the dispute concerns only the conversion difference, note that issuers may file for the currency delta rather than the full amount, and scope your response to that difference.

How to prevent 4846 chargebacks

Make DCC opt-in with an unambiguous choice screen, and store each cardholder's currency election with the order record.
Audit gateway currency configuration after every migration or new-corridor launch, and test with real foreign-issued cards.
Display the final currency and amount on the confirmation step exactly as it will clear, with no post-confirmation conversion.
Reconcile cleared currency against checkout currency in settlement reports so mismatches are caught in one day rather than one chargeback cycle.

Frequently asked questions

Is dynamic currency conversion against Mastercard rules?: No, DCC is permitted, but only with the cardholder's active choice. The violation occurs when conversion is applied by default, the choice screen is misleading, or the disclosure of rate and margin is inadequate. Documented cardholder election is your entire defense, so store it.
The customer is only upset about the exchange rate. Can they charge back the whole purchase?: Under this condition the issuer generally files for the currency difference when the underlying purchase is not disputed. If the full amount was charged back on a pure conversion complaint, challenge the scope in your second presentment along with the evidence of currency choice.

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