How do AI agents pay merchants? The 2026 guide to agent checkout and EUR settlement

The two ways an AI agent can pay

Every agent-payment standard shipping in 2026 falls into one of two families. Getting this split clear is the whole game, because the press treats them as competitors when they actually solve different layers.

• Delegated-card checkout — the agent never sees the card number. A payment provider issues a scoped, single-use token (or the user signs a cryptographic mandate), and the merchant charges it like any other card transaction. This is the model behind OpenAI and Stripe's Agentic Commerce Protocol, Google's Universal Commerce Protocol and Agent Payments Protocol, Mastercard Agent Pay and Visa's Trusted Agent Protocol.
• Native crypto payment — the agent pays in stablecoins directly over HTTP, with no card network in the loop. This is the model behind Coinbase's x402 and the Stripe/Tempo Machine Payments Protocol (MPP). A facilitator verifies the payment and settles it on-chain.

Cards suit consumer e-commerce and high-value, mandate-bound purchases like travel and procurement. Stablecoins suit API access, digital goods, compute and cross-border micropayments, where card fees and multi-day settlement do not work. Larger merchants are wiring up both.

What are ACP, UCP, AP2, Mastercard Agent Pay, Visa TAP, x402 and MPP?

Here is the full 2026 landscape on one screen, with who built each standard and what layer it owns.

Sources: Stripe ACP announcement, Agentic Commerce Protocol docs, Mastercard Agent Pay framework. See also our x402 vs MPP comparison.

What is Mastercard Agent Pay for Machines (AP4M)?

On 10 June 2026 Mastercard launched Agent Pay for Machines (AP4M), extending its 2025 Agent Pay program to high-frequency, machine-to-machine micropayments — transactions as small as a fraction of a cent, executed by agents with no human at the point of payment. AP4M adds four capabilities: credentialing (identity via "Verifiable Intent"), permissioning (programmatic spending limits), transacting (continuous high-frequency commerce), and guaranteed multi-rail settlement across cards, bank accounts and stablecoins. More than 30 partners joined at launch — including Coinbase, Stripe, Adyen, Cloudflare, RippleX, Polygon, Solana and BVNK — with agent permissions initially recorded on Polygon, Solana and Base.

AP4M matters because it confirms the direction of travel: even the card networks now settle agent payments in stablecoins, not only cards. But it is a global network layer. For a European seller the open question is unchanged — how the stablecoin becomes EUR in a bank account, under MiCA, with a verified payee and a known agent identity. AsterPay is that EUR/MiCA settlement leg: it slots underneath AP4M, x402 or MPP and pushes euros to the merchant's IBAN via SEPA Instant in under 10 seconds. AP4M decides whether an agent may pay; AsterPay decides how the euros land.

How does an AI agent check out and pay a merchant, step by step?

The mechanics are remarkably consistent across standards. An agent does not click through your checkout UI — it calls your API. The canonical sequence:

1. Discovery — the merchant exposes machine-readable product, price and policy data (Product, Offer and FAQ schema) and a manifest, e.g. at /.well-known/ucp, so the agent can find and parse the catalog without scraping.
2. Checkout session — the agent calls create_checkout, builds a cart, and the merchant returns line items, taxes, shipping and declared payment capabilities.
3. Authorization — the user (present) or the user's pre-authorized agent (absent) signs a mandate or receives a delegated, single-use payment token scoped to a maximum amount. In AP2 this is the dual-signed Cart Mandate: the merchant signs the price, the user signs the purchase.
4. Payment — the agent submits the token or the stablecoin payment to the merchant. The agent never holds the user's raw card credentials.
5. Accept or decline + settle — the merchant validates the authorization, uses fraud and trust signals to accept or decline, charges through its payment provider (or has a facilitator settle the stablecoin), and creates the order.

For the crypto path, the same five steps collapse into a single HTTP retry. The agent calls the endpoint, gets an HTTP 402 with payment requirements, signs a stablecoin payment, retries with the proof, and a facilitator settles it. We break that down in What is x402?

Is the merchant still the merchant of record?

Yes — and this is the single most reassuring fact for a business worried about agents. Across ACP, UCP, AP2 and x402, the merchant remains the merchant of record. As OpenAI and Stripe put it in the ACP spec, the business "receives a checkout request and secure payment credential details from the AI agent" and "can choose to accept or decline the transaction using payment and fraud signals, and is the merchant of record." The merchant calculates prices, manages inventory, processes the payment through its own provider, and owns the post-purchase relationship. The agent and the platform sit in front of checkout; they do not become the seller.

How does a European merchant actually get paid in EUR?

This is the question the card-centric standards leave open, and it is where most "agentic commerce" coverage stops. Authorizing a payment is not the same as settling it into spendable euros. Compare the last leg across rails:

The card rails get a European merchant euros eventually, but on card economics: roughly 1.4-2.9% in fees plus FX markup and multi-day settlement. The crypto rails are instant and near-free at the protocol layer, but raw x402 leaves a USDC balance on Base that the merchant still has to convert, value for VAT, and reconcile. Neither solves the actual European requirement: EUR in a bank account, with a clean reference, ready for accounting.

What the card standards leave unsolved for EU merchants

The ACP/UCP/card-network stack was designed in the US around card-based methods. Mollie, building agentic checkout for Europe, put the gap plainly: the current protocol standards are "initially US-centric and support only global, card-based methods (Apple Pay, Google Pay, Cards)" and this "is incomplete for European" commerce. Four things stay open for a European seller:

• EUR settlement — converting the payment to euros on a European bank rail (SEPA Instant), not a card timeline.
• MiCA alignment — when stablecoins are involved, the off-ramp is a regulated activity that must run through a licensed Crypto-Asset Service Provider.
• Agent identity and trust (KYA) — knowing which agent is paying, on whose authority, and within what limits. See Know Your Agent (KYA) compliance in Europe.
• Payee verification — resolving and validating the merchant's IBAN, including PSD2 Verification of Payee. See the Merchant Payment Endpoint.

AsterPay is built to close exactly these four gaps as a layer that sits underneath whichever checkout protocol the agent speaks. It is complementary to ACP and UCP, not a competitor to them.

Which rail should a merchant support?

Pick by what you sell, not by hype. A practical decision guide:

How a merchant becomes payable by agents in EUR

For the EUR-settlement leg specifically, the integration is short:

// Add x402 / MPP middleware to your API or checkout endpoint
app.use('/v1/*', x402Middleware({
  facilitator: 'https://x402.asterpay.io',
  price: '0.01',
  currency: 'USDC'
}));

// 1. An agent (any x402- or MPP-compatible) calls your endpoint
// 2. AsterPay verifies the agent (KYA), screens sanctions in <100ms
// 3. The agent pays in USDC; AsterPay converts USDC -> EUR
// 4. EUR lands on your IBAN via SEPA Instant in <10 seconds

The merchant never holds USDC; the agent never holds EUR. AsterPay is non-custodial — funds pass through licensed CASP partners under MiCA, never sitting on AsterPay's balance sheet. KYB onboarding takes about 10 minutes, after which payouts run automatically with no per-transaction KYC. Full mechanics in What is x402 EUR settlement?

Related reading

• What is x402 EUR settlement? — the definitive guide
• x402 vs MPP — which agent payment protocol should you support?
• How do AI agents pay any business? The Merchant Payment Endpoint (MPE)
• Know Your Agent (KYA) compliance in Europe
• What is an x402 facilitator?
• How AsterPay compares — Stripe, Wise, BVNK, raw x402

Have a correction or want this page to cover a different angle? Email [email protected]. We update this page every quarter.