How is the Zakat calculated on a salary deposited in a usurious bank since January 2008, when January 2009 arrives, and is it better to withdraw it or leave it in the bank due to the unavailability of Islamic banks?

Fatwas have been previously issued concerning the zakat on salaries, and the usurious increase, called interest, is ill-gotten wealth that is not subject to zakat and must be disposed of. It is impermissible to deposit one's salary in a usurious bank if it is possible to deposit it in an Islamic bank. However, if one is compelled to do so, or if no Islamic banks exist, it is permissible to the extent of necessity, provided the money is placed in a current account rather than a savings account, and any interest earned is disposed of. It is preferable to withdraw the entire salary if no harm results from doing so.