Is zakat due on both capital and profits, or on profits only, and for one time or for each year, after recovering an amount that was invested in a real estate company for years without paying its zakat?

The money saved in the investment company, if it reaches the nisab and a year has passed over it, zakat is obligatory on it along with the profit every year. It is obligatory to hasten to pay the zakat for the past years before buying the house.