The Agentic Commerce Protocol is an open standard for agent-initiated checkout, co-developed by OpenAI and Stripe and released in late September 2025.
It defines how an AI agent (such as ChatGPT) passes a buyer's order and payment details to a merchant's backend, so the merchant can accept the order, charge through its own payment provider and remain the merchant of record.
ACP underpins Instant Checkout in ChatGPT; PayPal supports payments for merchants using it.