My grandfather wants to gift me his property using a gift deed. How much stamp duty will I need to pay? Also, if I register the deed legally, can anyone challenge it in the future?

The stamp duty on a gift deed varies by state and the property’s value. You can check the relevant state government website for the specific rates. While a legally registered gift deed is generally strong, it could be challenged if it’s proven to be fraudulent or if your grandfather’s mental capacity was compromised at the time of the gifting.