Open a checkout session

Open a checkout session for one or more (up to 10) of your own billing periods. `customer_id` is optional and, if sent with a value, must be a customer already recorded on your account; omit it, or send it null or blank, to have the buyer enter their full name, email, phone and address at checkout. Each item's price is snapshotted at creation, so a plan edited afterwards cannot change what the buyer already saw. If two items resolve to the same product (e.g. via different `pbp_id`s), only the last one is kept. `return_url` is required and is where the buyer lands after paying. Send the returned `checkout_url` to the buyer to collect payment. This is the one rate-limited endpoint on the partner API — 20 sessions a minute per account by default, answered with 429 once exceeded.

curl -X POST "https://example.com/checkout-sessions/" \  -H "Content-Type: application/json" \  -d '{    "items": [      {        "pbp_id": "pbp_3n9k2x"      }    ],    "return_url": "https://partner.example.com/orders/1234"  }'

{  "public_id": "cks_3n9k2xQ7m",  "expires_at": "2026-07-03T10:45:00Z",  "checkout_url": "https://app.suqo.ai/checkout/cks_3n9k2xQ7m"}