A structured reference is a payment reference that follows a defined format instead of being free text. The payee generates it, prints it on the invoice or bill, and asks the payer to quote it exactly when paying. Because it includes check digits, the payer's bank can detect a mistyped reference before the payment is sent.
The international standard is the ISO 11649 creditor reference, which starts with the letters RF followed by two check digits and up to 21 further characters. Several European countries have national formats that serve the same purpose. In a SEPA Credit Transfer and other ISO 20022 payments, the reference is carried in the structured part of the remittance information and must be passed to the payee unchanged. The payee's accounting system reads it and marks the right invoice as paid without manual work.