I recently did a transaction and tried redeeming the reward points, while everything happened fine initially after 2-3 days I got an emails rating that the reward point redemption failed.
On sending a query to IDFC, this was their response -
With reference to your below email, as checked, the reward points on your credit card number ending with ****4533 are 32037 points; the transaction value for these reward points is 8009.25 INR. Hence the reward points were not redeemed on the transaction of 8,075.52 INR. However, if you wish to redeem points against the transactions, we request that you perform the transaction of 8009.25 INR as per the reward point balance.