Cenvat credit reversal

Whether cenvat credit is to be revesed if we are deducting discount on final payment from the purchase invoice on which we have taken credit ? For eg. Purchase invoice was of Rs. 1,00,000 and excise duty was Rs. 10,300 and final payment on this invoice was only Rs. 90,000. Now whether credit will be reversed to the extent of Rs. (10,300 * 90,000/100,000) ?