Capital gains

You will have to find the value of that building as on 1981.

You will have to compute the cost of constructing additional floors and in which year and how much was your share.

The indexed cost of acquisition will be year 1981 at 100 for the fair market value of that building

The indexed cost of improvement will be the year in which additional fllors were completed for the cost incurred by you.

Then, the indexed cost of acquisition/improvement will be substracted from sale value giving you the capital gain.

fair value as on 1st april 1981 is required for that,

and capital gain is calculated as below,

         full value of consideration                     =46lacs

less:      exp incurd in conn with such sale =xxxx

less:indexed cost of aquisition                     =xxxx

less:indexed cost of improvement               =xxxx

in ur case indexation on improvement is not available becuse it is done before 1981,

correct me if i am wrong,

thank u.