कॅपिट्ल गेन्स

In July, I had sold my share of flat to my sister who is the joint owner of that flat. We did it legally i.e Registration of Trasnfer Deed. I had some capital gain. My query is for re-investment of capital gains, can I re-invest and write-off the same in my existing flat which we(me+husband) booked 2.5 - 3 years back but yet to take possession of the same. The flat was under construction and now ready for possession. The new flat is purchased on loan so we will be paying off loan of the flat.