the Fatwa Department Research Committee - chaired by Sheikh `Abd al-Wahhâb al-Turayrî
As a general rule, Zakâh is due on the money for every year that it is in your possession for the full duration of that year, as long as it is of sufficient value to make you liable to pay Zakâh.
Therefore, if you have the legal right to withdraw from the account or cancel the contract early and receive your money, then you will have to pay the Zakâh on it promptly each year. This does not mean that you actually must draw the Zakâh from the account itself. You may pay the Zakâh from other monies in your possession.
If the money is effectively on loan to the investment firm whereby you do not have the ability to draw from it for the three-year period, then you do not have to pay the Zakâh annually. You may pay it yearly if you like or postpone payment until the time that the instrument matures and the firm returns the money to you.
However, when the money is returned to you after three years, you will be liable to pay the full three years' Zakâh that has accrued against it.
Source: Islam Today