Credit note - gst

Dear Team,

we are manufacturor of some products, and we are selling thru distributor - dealer chennal, we are also running some festival schemes, like for sale achievement we will give some rewards.

this rewards are by way of issuing credit notes only. 

If my memory is correct, we should charge GST for the achieved amount along with the credit note, 
if so, how will we show this credit notes thru GST returns, and what will be the impact if the receiver failed to file the relevant debit note?

please help me in this regards
- Ashok