Greetings subscription features in a custom app for charging users(not merchats) to subscribe to products (product subscription) does shopify bill the user on the renewal date or we have to do it ourselves. because I have a an app where a user purchased a subscription but was not billed on the renewal date
that not what I meant I meant billing the users for each interval of the duration of the subscription via the api
Hello.
I’m Max - Support representative at Seal Subscriptions.
What subscriptions app are you using currently from which you encountered this issue?
Generally, if the app you are using has the “auto-charging” functionality for other customers, they should get billed automatically.
Kindly let me know, so that I can assist you further. 
we built or own custom app and users purchase product subscription with the shopify graphql api