Capital gain tax -pls. reply

Yes no problem with that. Take an advance and start constructing.The key date is the date on which you register the property to the buyer. The completion of house can be within 3 years of selling the old house. There is a small legal hitch here as constructing a house property before sale is not specifically mentioned in the section, but since you will complete the construction only after sale of the old flat t is OK. make sure you get completion certificate from local authorities after the sale deed is executed for the old flat