camt.026
The ISO 20022 message in which a bank admits it has received a payment but has no idea what to do with it.
Its formal name is UnableToApply, and it belongs to the exceptions and investigations family. The textbook case is an incoming payment where the beneficiary account does not exist, the name does not match, or the remittance information is too thin to book the funds. Instead of a free-text message that a human has to read, the bank sends a structured query back up the chain, with a code saying what is missing.
The answer arrives either as a camt.028 carrying the additional details or as a camt.029 closing the case. The whole point of structured investigations is that machines can pair question with answer, which assumes every party actually fills in the fields. That assumption is where things usually come apart.