GST: How does the anti-profiteering law work under the new tax regime?

Govt is yet to release norms regarding various aspects relating to the anti-profiteering provisions

I have certain queries regarding supply of goods. In our case, we normally give quantity against quantity offer: Say, if you buy 100 boxes of product A, then you will get one box of product B.

How should we present the free quantity supply on the tax invoice? Should we show the product price and then give 100 per cent discounts with zero taxable value, so that product value becomes zero or we don’t need to show product price in the tax invoice? Which is the best way?
 

Is it necessary to mention any scheme numbers on the tax invoice and