After a paid x402 request, the seller answers with a PAYMENT-RESPONSE header (X-PAYMENT-RESPONSE in x402 v1). Paste it here to see which on-chain transaction it points to, whether that transaction exists and succeeded, and which USDC moved from whom to whom.
Paste the header
Where to find the header
curl: add -i to the paid request and copy the value after payment-response:.
JavaScript:res.headers.get('payment-response') (or x-payment-response for v1 sellers).
A browser: developer tools → Network → the paid request → Response headers.
What it tells you
In plain x402 one paid request is one signed authorization, one settlement and one transaction. The header names it: transaction, network, payer and success.
A hosted checkout (such as a payment session) adds its own ids on top; those live in that provider's backend. The transaction hash is still the link to the chain.
Not found? Check the network. A payment for Base won't show a transfer made on Solana, and the other way round.