An add-on is a charge billed each billing period in addition to a subscription’s base charge. Each plan may have one or more add-ons associated with it. You’ll define your add-ons when creating or editing plans.
Subscribers can use the Hosted Payments Pages to view and select from the available add-ons. API users can specify add-ons when creating or updating subscriptions.
Add-ons can be customized with the following properties:
Describes your add-on and will appear in subscribers' invoices. (255 characters limit.)
Identifies the add-on in Recurly. Must be unique per plan. (50 character limit.)
Amount to bill for this add-on
Whether or not a customer can choose their own add-on quantity.