Proof of payment can be a signed receipt, transaction identifier, cryptographic authorization, ledger record, or protocol-specific token that links a payment to a request. The resource server verifies the proof before granting paid access.
Evidence of submission is not always evidence of final settlement. Systems must define the required confirmation state, prevent one proof from being reused for multiple resources, bind it to the correct amount and recipient, and handle retries without charging twice.
ELI5
Proof of payment is evidence that a specific bill was paid or that an approved payment reached the required stage. Software checks the proof before releasing the resource that was priced.
For example, after an agent sends a small payment, it can retry the data request with a signed receipt or transaction reference. The service verifies that the proof matches the amount, recipient, and exact request instead of trusting the agent's claim.
