Geetha,
As JP asked, please elaborate, give an example describing the entire process.
The tricky part for me is -
Your company wants to sell 10pc and with it give 2pc free.
Your company tells its vendor to delivery 12pc. The vendor sends a bill to your company. Is this for 10pc or for 12pc?
Would vendor agree to give your company 2pc free?
In 3rd party standard SAP process, what ever qty the vendor has delivered to the customer (of your company), those many qty invoice verification is done. And based on that, the customer makes a bill to its customer.