payerId

PayerId is a unique identifier assigned to the payer, the individual or entity that initiates a payment, within a payment processing system. It allows payment providers and merchant platforms to reference the payer across transactions and sessions, enabling account linking, reconciliation, and fraud checks. The payerId is distinct from other identifiers such as the transaction ID, the merchant's own customerId, or the processor's account number.

In API design, payerId is often exposed as a string field in responses or requests. The exact name and format vary by provider; some APIs use payerId, others use payer_id or similar.

Use cases include recurring payments where a payer is repeatedly charged, refunds or chargebacks tied to the original payer, and marketplaces that collect from a payer on behalf of vendors. The identifier helps maintain continuity of the payer across multiple operations and platforms involved in a payment flow.

Security and privacy: Payer identifiers should be treated as personal data. Access should be restricted; transmitted over TLS; not logged in plain text. Appropriate data handling and retention policies should be observed, and sharing of payer identifiers should follow applicable regulatory and provider-specific rules.

Examples: In PayPal's REST APIs, the payer_id field identifies the PayPal account used to approve the payment. Other providers may use different field names but maintain the same concept of a payer-level identifier.