Excise duty-dealers return filing & invoice issue format

Regarding Excise return filling of dealer[not manufacturer], and invoice should issued to cutomer[i mean in which format]?

One of client is just registered under excise duty. As he is dealer of gas, there is no liability attarcts. My question is, How to issue invoice to customer?? How to calculate excise on goods[at what rate]??.

And about quarterly return filing... How to fill quarterly return???.

Please reply with ur answere as early as possible...