A payment reference is a code or short piece of text sent with a payment to identify what it is for. Payers typically use it to quote an invoice number, customer number or policy number, so that the payee can recognise the payment and apply it to the right account. Banks and payment systems also attach their own references, such as transaction identifiers, to track the payment through the chain. Domestic systems often allow only a short reference, such as 18 characters for UK Faster Payments, while ISO 20022 messages provide richer remittance fields, including structured references such as the ISO 11649 creditor reference. Messages also carry a separate end-to-end identifier and, in cross-border payments, a unique end-to-end transaction reference (UETR). Accurate references are central to payment reference matching and payment reconciliation; when they are missing or wrong, payments sit unapplied and need manual investigation.