Budget billing in SAP ISU

Hi Experts,

I'm new to FICA. I've lots of confussion in budget billing plan; for example :-

1. How meter reads play role in calculating budget billing amount.

2. How due date and posting date determined for budget billing amount.

3. If meter reads will not present in system, i.e. next day after move-in ( move-in read is 0), how budget bill amount will be calculated.

4. If we process invoicing for any periodic meter read, how budget bill will effect ? How invoice amount of periodic meter reads is related to budget billing amount.

etc.

Kindly explain complete procedure and process of Budget billing plan.

Thanks in Advance !!

Thanks & Regards,

Dipesh Kumar