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Can we pass existing customers via plan-based URL in PC 2.0?
Is it possible to create a checkout page using the Plan based URL syntax and pass an existing customer ID?
The customer[id] param can only be passed via API for authentication. It is not supported via the Plan based URL. Plan-based URL works as expected when customer[id] param is not passed.
If you want to create a subscription for an existing customer, then you can make use of cart customization via Chargebee JS
Cart Object - Checkout & Self-Serve portal
Example - Checkout & Self-Serve portal
OR they can use our Hosted Pages API
API docs - Hosted pages | Chargebee API documentation