I get a lot of IS-U questions and I'll use this post to start group them in some way.
Billing:1) Can we use Payment scheme with DPC back billing ?
A: As far as I know you can use DPC with Budgetbilling ( I guess with payments plans as well because they are a type of budgetbilling) starting with version 4.7.2
2) In DPC should estimate consumption during billing ? If yes, then what is the advantage?
A: If you estimate the consumption durring billing then you will not have any Meter Reading Result in the system (no entry in EABL, EABLG table). The system is estimating a consumption and then based on the consumption it is determining a reading. If you need to print estimated readings on your invoice that would lead to inconcistencies from one billing perioad to another. The advantage is that you do not store the Meter Reading Result in the database.
3) Is UTILIT98 starting a workflow!
Yes it is starting an workflow. Actually it is triggering the event BillingEvent01 of BILLDOCAUT business object. Then you can link your workflow to this event. You can use it to send alerts or to start a business process as an action to a billing result.