A payment message is a structured electronic communication that carries the information needed to make, confirm, report or reverse a payment. It is how one financial institution tells another, or a payment system, to move money. A message does not itself move funds: it is the instruction and record, while the money moves through settlement between accounts.
Each message follows a published standard that fixes its fields and their order, so that systems can process it without human reading, the wider subject of payment messaging. A customer credit transfer between banks is typically a pacs.008 message under ISO 20022, which is replacing the older SWIFT MT103 for cross-border payments. Card authorizations use ISO 8583. A typical message names the payer and payee, their accounts and institutions, the amount and currency, the value date, a unique reference and any remittance details. The customer's original payment instruction to their bank is the first message in the chain.