Decline reasons that don't fit neatly into the categories above, or that are scheme-specific edge cases.
A "Do Not Honor" decline is a catch-all response from the card issuer meaning it chose not to approve the transaction, without specifying the exact reason. It can stem from risk rules, account restrictions, or discretionary fraud checks the issuer does not disclose to the merchant.
"Refer to Card Issuer" is a generic response instructing the merchant that only the cardholder's bank can explain or resolve the decline. It's one of the most common catch-all decline codes merchants encounter, alongside "Do Not Honor," and gives no specific reason for the refusal.