38 codes that cover most of what an originator sees. Each one carries the decision: retry or stop, how long the receiving institution has to send it, what the guidance rests on, and when it was last checked.
On a rail fact, every detail line names the section or instrument it rests on and whether that is a rule, a law, operator guidance, or observed practice.
Not yet covered: partial list: these are the 38 DE 39 decline values that the Transaction Processing Rules name in section 4.5.5 (Table 23); Mastercard's full set of response codes and their valid pairing with Merchant Advice Codes are in the Dual and Single Message System technical specifications, which are not public to Orca; non-decline DE 39 values that the Transaction Processing Rules mention (00 and 85 for an open account, 10 partial approval, 06, 17 and 32 on reversals, 34 for a merchant fraud cancellation) and the value 31 named only in the Europe issuer failure-rate rule have no record; the meaning of each code is taken from Mastercard's label in Table 23 and from the rules that name the code; the definitions in the technical specifications have not been read; Table 23 sorts the codes for transit debt recovery and first ride risk claims only; how an issuer should choose among them, and the common decline guidance in the Enhance Digital Commerce Approval Rates Operational Guide, are not public to Orca; in the EEA, the UK and Gibraltar a customer may route through a registered switch of its choice, and the response codes that switch defines (including its soft decline for Strong Customer Authentication) are not described here.