Index rate of capital gains

hello everyone...

my client has received notice sec 148 for income tax payable on capital ....
he purchase property in 1997 and sale the property in 2014
so myquestions is which index rate chart is use( old index rate chart of base rate 100 of 1981 or new of base rate 2000 as 100 )for calculations of capital gains in year 2021 as old revise returns AY 2014 _ 15