Chargeback reason codes are the standardized codes issuers attach to every dispute to state why the cardholder is challenging the charge. Visa groups its codes into four numbered categories, fraud, authorization, processing errors and consumer disputes, while Mastercard uses its own four digit codes covering the same ground.
Why it matters
The reason code is the rulebook for the fight: it dictates what evidence is admissible in representment, what time limits apply and whether a win is realistic. It is also intelligence. A cluster of fraud codes points at your checkout controls, a wave of “product not received” points at fulfilment or expectation gaps, and codes tied to subscriptions point at your negative option billing flow. High risk merchants who tag every dispute by code and review the mix monthly usually find their next prevention project written in the data.