- Add a 
credit_typecustom field to the credit entity and set the relevant value on each object. For example,free_trial. - Navigate to Notifications > click Add Notification.
 - Name the notification.
 - Select the Contract credit balance notification type and enter a $0 value.
 - Click Advanced filters > select 
credit_typeas the custom field key and enterfree_trialas the value. - Select the customers to whom this notification should apply.