How is zakat paid on shares purchased to benefit from their profits, which have not distributed profits and have decreased in value?

Zakat on shares is due based on their value at the end of the Hijri year, not their purchase value. If the shares are for speculation or profit, then zakat is due on all of them. However, if the shares are in fixed assets that are leased out, then zakat is due on the profits if they reach the nisab and a year has passed over them, and there is no zakat on the principal capital.