Who sends the money back on x402?

The x402 FAQ says settled exact or upto payments have no chargebacks. A refund is a new transfer back to the payer address from the settlement record.

Who handles an ACP refund?

The Stripe seller guide says an existing Checkout Sessions or Payment Intents refund flow works for agentic checkouts. Disputes are handled on the Transactions page or through the dispute response docs.

What does not documented mean here?

Not documented means the cited page does not state a refund or dispute path. The line names that page and the day it was read.

Does this page choose a rail?

No. It quotes each rail's own page. It does not rank the rails.

Concept

Who handles a refund when an agent pays

A refund follows the page for that rail. On x402, settled exact or upto payments have no chargebacks, and a seller sends a new transfer. On MPP, the service returns a charge, or an unclaimed session deposit returns at close. On ACP, the business uses its Stripe refund flow. A silent page is marked not documented. Checked 2026-10-26.

Last verified 2026-10-26

Sources

How to read this

A refund on this page is whatever the rail's own page says happens after an agent has paid. Some pages name the business, the seller, or the network that moves the money back. Some pages name a record a network can read in a dispute. Some pages do not mention a refund or a dispute at all. Those notes say not documented, with the day the page was read.

The notes below are the refunds and disputes dimension from the gaps file. Each line keeps its source. This page does not add a handler the source does not name, and it does not rank the rails.

Gaps index · Gaps JSON

Agentic Commerce Protocol

The Stripe seller guide says an existing Checkout Sessions or Payment Intents refund flow works without changes for agentic checkouts. Refunds and disputes are managed on the Transactions page or with the Refunds API, and disputes use Stripe's dispute response docs.
Stripe docs: Handle orders from agents · Read 2026-10-26

AP2

The AP2 FAQ says that in a dispute, the network adjudicator can compare the user-signed Checkout Mandate with the dispute. It also says the Checkout Mandate and Payment Mandate are signed records that support that review.
AP2 FAQ · Read 2026-10-26

Coinbase Agentic Wallet

The Agentic Wallet FAQ says x402 payments are instant and onchain, and refunds depend on the service provider. It says to contact that provider directly.
Coinbase CDP docs: Agentic Wallet FAQ · Read 2026-10-26

L402

Not documented as of 2026-10-26. The L402 page describes paying a Lightning invoice and presenting the preimage. It does not describe a refund or a dispute.
Lightning Engineering docs: L402 · Read 2026-10-26

Machine Payments Protocol

The MPP refunds page says MPP does not define a dedicated refund protocol. In the charge flow, the server sends funds back to the client address on the Credential source field. In the session flow, unclaimed funds return to the client when the session expires or closes.
MPP docs: Refunds · Read 2026-10-26

Mastercard Agent Pay for Machines

Not documented as of 2026-10-26. The 20 October 2026 announcement describes payment vouchers, budgets, and later redemption. It does not describe a refund or a dispute.
Mastercard: Agent Pay for Machines in action, 20 October 2026 · Read 2026-10-26

Nevermined

The Orders page says Phase 1 has no refund endpoint. A refund is issued on the Stripe side by Nevermined, and you contact Nevermined to refund an Order. A chargeback moves the Order to disputed. A won dispute returns it to paid, and a lost dispute stays disputed.
Nevermined docs: Orders · Read 2026-10-26

PayAI x402 facilitator

The batch settlement page says the server can cooperatively refund a customer's unused channel balance at any time. The customer can start a timed withdrawal, one to 24 hours under PayAI's policy, as a unilateral fallback.
PayAI docs: EVM batch settlement on Base · Read 2026-10-26

px402

The px402 overview says that if a merchant's processor fails to collect a payment, the agent's coins are restored automatically.
px402 docs: What is px402 · Read 2026-10-26

Skyfire

The Verified Service Guarantee says a buyer may submit a dispute to support within 5 days of a pay or kya-pay token charge with a green-tagged Verified Seller. If Skyfire deems the dispute valid, the full amount is restored to the Skyfire account balance.
Skyfire docs: Verified Service Guarantee · Read 2026-10-26

Stabletrust API

Not documented as of 2026-10-26. The agentic API page describes confidential deposit, transfer, and withdraw. It does not describe a refund or a dispute.
Fairblock docs: Stabletrust API · Read 2026-10-26

Stripe link-cli

The Link wallet page says retrieve shows refunds and payment events, and refund_details carries the amount, currency, state, and creation time when a refund exists. Canceling a recurring request revokes its credential and does not cancel the subscription with the seller.
Stripe docs: Use Link wallet to pay online · Read 2026-10-26

Stripe Treasury for agents

Not documented as of 2026-10-26. The Treasury for agents page says live money movement needs review and approval. It does not describe a refund or a dispute workflow.
Stripe docs: Treasury for agents · Read 2026-10-26

Universal Commerce Protocol

The UCP order specification says an order can carry post-order Adjustment entries. The type is an open string, and the spec's examples include refund, dispute, and cancellation. Totals are signed, and a negative amount means money returned to the buyer.
UCP specification: Order capability, 25 August 2026 · Read 2026-10-26

Visa Trusted Agent Protocol

Not documented as of 2026-10-26. The getting started page describes signature checks a merchant uses to recognize an agent. It does not describe a refund or a dispute.
Visa Developer Center: getting started with Trusted Agent Protocol · Read 2026-10-26

x402

The x402 FAQ says payments made with exact or upto are irreversible once settled, so there are no chargebacks. To refund, send a transfer back to the payer address from the settlement record.
Coinbase CDP docs: x402 FAQ · Read 2026-10-26

Questions

Who sends the money back on x402?: The x402 FAQ says settled exact or upto payments have no chargebacks. A refund is a new transfer back to the payer address from the settlement record.
Who handles an ACP refund?: The Stripe seller guide says an existing Checkout Sessions or Payment Intents refund flow works for agentic checkouts. Disputes are handled on the Transactions page or through the dispute response docs.
What does not documented mean here?: Not documented means the cited page does not state a refund or dispute path. The line names that page and the day it was read.
Does this page choose a rail?: No. It quotes each rail's own page. It does not rank the rails.

Sources

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