Vat Treatment

WHAT SHOULD BE THE VAT TREATMENT DONE BY SELLER OF GOODS.

1. whether we have to effect vat(reverse VAT)  while issuing Cr.Note note to purchase for price drop.

2.whether we have to effect Vat(reverse vat) while allowing discount Separately(i.e., not at the time of preparing Invoice) to party  for goods sold by issung Credit note.

3. Goods sold returned Cr. Note isued by seller after deducting 10% of deduction due to goods found defective