it is not compulsory to purchase property after selling one .Tax provisions provide for exemptions for capital gains from the sale of a house if the taxpayer invests the gains in a residential property within two years from the date of sale or constructs another house within three years.
the sale of a property involves short-term capital gains tax if it is sold before the completion of three years of purchase. Such gains are taxed at the same rate as applicable to any other income of a taxpayer.
However, if the property is sold after three years of purchase, the resultant gains — known as long-term gains — are taxable at a fixed rate of 20%. That apart, the taxpayer is entitled to avail the benefit of an inflated cost of acquisition of the property as prescribed. Also, you might be able to avoid paying tax on long-term capital gain arising from sale of the house, and also have an option to reducing the tax burden.