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I don’t see the option to include prorated credit. Where does it appear?

Summary

When you import the subscriptions and invoices into Chargebee, the parameter use_for_proration should be passed as True. If this is passed as False during import, there will be no option for Proration while canceling or changing the subscription. 

Info: Proration applies only to the invoices that fall within the subscription’s current term

The use_for_proration attribute enables proration for the current term invoices. Option 

true = enable

false = disable

If you have imported invoices or subscriptions with use_for_proration as false or no value, you should apply for the prorated credits manually (by calculating it at your end). 

Warning:

1.This parameter is present only in Import invoices bulk operation or APIs
2. If the invoices are already imported without setting the use_for_proration as true then, you can re-import the invoice after deleting the existing one

Related articles and Documentation

Pro-ration logic in subscriptions 

Where is the credit card stored for recurring transactions? Is it safe?