How do I create a credit for a prior periods where revenue has already been recognized?

To create a credit for a prior period when revenue has already been recognized, create the Credit and adjust future RSLs of a Subscription Charge to match. Read more about creating a credit. 

To reduce deferred revenue with a Credit, the GL account selected when creating a Credit should be the Deferred Revenue Account that needs to be reduced. Future Revenue Schedules also must be adjusted when the Credit is being applied to a prior period where revenue has already been recognized in the amount of the applied credit.