Creates a shopping cart. The cart is the first step of the online payment
flow: add items, then create a payment request on the cart to obtain a
checkout URL.

Important Notes

• Requires carts:write scope.
• Online payments must be enabled for the company to complete the flow. Carts can be created regardless, but payment request creation fails when online payments are disabled.
• The cart always belongs to the authenticated company; any company_id sent in the body is ignored.
• To sell a service and book it in the same flow, send an item with item_type: "service" and a single instance { "instance_type": "booking", "reference_id": null, "data": { "start_time": "...", "provider_id": ... } }. The booking is created automatically when the payment request is created, and released automatically if the payment request expires or is cancelled.
• data.start_time must be an ISO 8601 datetime in UTC (Z or +00:00, e.g. 2026-08-01T13:00:00Z). Other offsets are accepted here but rejected when the booking is reserved at payment-request time (invalid_start_time).
• data.creative_source cannot be set: it is always connect for the public API (any value sent is overridden).
• Carts expire after 24 hours.
• Item validation errors (400/422) from platform-sales are passed through unchanged; see the platform-sales carts documentation for the full dictionary.
• Business errors proxied from platform-sales use legacy single-key codes (e.g. cart_not_found, invalid_start_time, creative_source_not_public) rather than the {error, detail} shape used by connect-level errors (auth, scope, rate limit).

Errors Dictionary