Dear Querist,
Your father will be liable to pay Long-Term Capital Gains tax on the capital gain, not on the full sale value. The exact tax can be calculated only after reviewing the purchase date, sale date, and other relevant details.
Also, your father need not sell the property. He can gift it to you, which may result in significant tax and stamp duty savings, depending on the applicable State laws. If he requires funds, you can separately gift the money to him, as gifts between specified relatives are exempt from income tax.
For a more detailed review of your case, you may book a phone consultation.
CA Shubham Goyal