Stamp duty applies during property sale and purchase. It is usually used in context of home loans or home purchase, where you as a buyer pay a stamp duty to the state government, which may amount up to 8% of the property’s market value. The exact percentage differs from state to state, and you can get a deduction on what you have paid as stamp duty when you calculate your income tax.
For instance, if the property cost as per the circle rate is ₹40 Lakhs and the stamp duty rate is 7%, your stamp duty amounts to (7/100 X 40) ₹2.80 Lakhs.