Chartered Accountant
5010 Points
Joined March 2020
Take the base year for indexation as 2001 because the property was built by your father in 1985.
For calculation of Capital gain, the cost of the previous owner is indexed to determine the profit or loss on the sale of the property.
As mentioned above, you don't know the price spent for the construction of the property. Since the property was acquired by your father prior to 1 April 2001, there is an option of taking the actual cost of acquisition or fair market value as on 1 April 2001 for calculating the indexed cost of the property.