Yes, you can use Section 54F to claim tax free long term capital gains. You should however before the due date of filing your iTR, which could be 31 July 2018 if you are not subject to any audit, deposit the underutilized money (Net sales less amount paid for the plot of land you sold) from sale into Capital Gains Account Scheme with a bank if you still have not bought the land by that date. This account is valid for max 3 years. You would need to utilize the amount of the deposit for constructing, including land price, which should be completed within 3 years from the date of sale. You will need to file ITR. So effectively the land should be bought by the last date of the return filing and then you will not have any tax liability as you would have used the entire amount of sale for buying land.