Receive the chargeback notification and identify the reason code from the DE 25 (Message Reason Code) field; Mastercard uses a four-digit code scheme (e.g., 4853 Cardholder Dispute, 4863 Cardholder Does Not Recognize, 4837 No Cardholder Authorization)
Map the reason code to the correct dispute category: 4853/4855/4859 are service/goods dispute codes; 4837/4840/4863 are fraud codes; 4808 is an authorization-related code; each category has different evidence requirements and time limits
Determine your response window: first chargeback responses are generally due within 45 calendar days of the chargeback date; second presentment (arbitration chargeback) has a shorter window — verify exact timelines with your acquirer as they may apply tighter internal deadlines
Assemble reason-code-specific evidence: for 4853 (not as described), provide product/service description and proof of delivery; for 4837 (no authorization), provide AVS/CVV match data and shipping confirmation to the verified billing address
Submit your representment through your acquirer's dispute portal; include a rebuttal letter clearly stating the applicable Mastercard rule being cited in your defense
Known gotchas
Mastercard arbitration (second chargeback) costs include filing fees that are forfeited if you lose; assess win probability before escalating to arbitration
Reason code 4808 (authorization-related) disputes often arise from expired authorizations or approval code mismatches; these are largely preventable through proper authorization practices rather than defensible after the fact
Mastercard updates reason codes and rules annually; always reference the current Mastercard Rules and Chargeback Guide rather than cached internal documentation
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp