Question:
An amendment Quote to change the billing period of a charge Tier 2 Channel Fee - 30 Days Storage from Month to Quarter was created from SFDC and sent to Zuora.
When previewing the Invoices the first invoice for 7/1/19 has the billing period as Month and service period for 7/1-7/15 and the 8/1/19 invoice has two entries for the particular charge, one for a service period of 7/16-7/31 and then 8/1-10/31.
Why is the charge prorated and split between the two invoices? The first invoice should be 7/1-9/30.
Answer :
On checking the Preview of the Subscription mentioned in the request the explanation of the split between the invoices is as follows :
The Charge Tier 2 Channel Fee - 30 Days Storage is amended from the billing period Month to Quarter on 7/16/2019. ( Start Date of the Amendment Quote )
As the settings for proration in the tenant is as follows : 
Due to the above settings :
Tier 2 Channel Fee - 30 Days Storage is billed for the billing period Month from 07/01/2019 - 07/15/2019.
- Unit Price = 30.00 /Month
- Quantity =14
- Subtotal = 420 * 15/31 = 203.23
Since the Change of the billing period as Quarter is effective from 07/16/2019it is billed as a separate invoice from 7/16/2019 - 7/31/2019
- Unit Price = 30.00 /Month
- Quantity =14
- Subtotal = 420 * 16/31 = 216.77
Once this is normalized it gets billed as per the Quarter.
You can check this by previewing it till the End of Term.
