Hello, I’m a chinese devepler, I can use PaymentApi to pay an order in Sanbox environment, use CatalogApi,SubscriptionsApi to create a scheduled payment in Sanbox environment. I know migrating Sandbox services to Production Account steps.
In Sanbox environment , I can create customer in Dashboard .
Now, I want to know how to get customer id in Production environment? Thank you!
With the Customers API you can call ListCustomers to get the customer_ids for your production environment. 
Can customers automatically create in production environment ? If I use Customers API create customer, How can these customers deduct fees automatically? How does SubscriptionsApi bind to these customers by Customers API create in squareup server?
It will all depend on you’re use case. Are you going to be creating subscriptions with the Subscriptions API? If so you will need to collect customer information at some point in order to have customers in production.