Hello Mr. Vivek,
I understand from your query, you are buying an flat (not self construction undertaken). In this case scenario, my view is :
a. You should purchase a residential house within the period of two years after the date of the transfer of the original asset.
b. It is also held in several cases that Investment in the new residential property is good enough to claim tax exemption. Occupancy / occupancy certificate is not a mandatory requirement to fulfill the period of two years stated in point a above. Hence if you are unable to occupy due to non-possession within 2 year period window, it does not mean you are not entitled to tax exemption as you have sufficient proof to prove that you have invested in the property.
c. Thirdly, delay in delivery of possesion by the builder does not in any way penalise the tax assessee from claiming tax exemption as is held in several tax cases.
Hope this meets your requirement.
Balaji Srini FCA., LL.B.