Hi,
a right to obtain conveyance of immovable property is "property". Therefore, if the booking agreement and allotment terms and conditions of the builder gave a right to obtain conveyance on the said flat, the property after fulfilling certain conditions, that itself becomes "an asset" under the Income-tax Act. Date of investment in the property will be the date of allotment of the residential flat and the payment of installment is a follow up action. Allotment is a sufficient compliance for getting the benefits, even if the taxpayer has not paid all installments due under the said scheme.
so it is crucial to check what is the date of agreement and if conveyance is being obtained in the said property, if it is may 2013, then it falls under long term capital gain and you can indexed the cost of purchase. i believe then in your case there will be a loss on sale of flat.
otherwise it will be short term capital gain. then there is no profit arising in your case. then no capital gain , but still you need to file a return showing sale of flat under capital gain.
And yes you can go head with sale of flat .with the above mentioned documents. Do make a sale agreement.
Buyer is required to deduct 1% TDS in case of seller is resident indian or 10% in case of NRI seller. if the value of purchase property is more than RS 50Lakhs.