Presentations delivered through x401 to an organization billed by invoice, with no card or bank account on file, omit the signature segment of both the Issuer-signed JWT and the Key Binding JWT. The Key Binding JWT header carries a critical proof.com#sig-1 parameter whose value is the id to send here. Authenticate with a private_key_jwt client assertion from the OAuth Application that requested the presentation, with aud set to this endpoint URL.

When the transaction is not yet paid, the first call answers 402 with x402 payment requirements (https://www.x402.org) for the transaction price; repeat the request with the PAYMENT-SIGNATURE header to settle and receive the signatures. A 409 means the transaction is still being finalized: retry after the Retry-After delay. Records expire one hour after the presentation.