Nisab can be calculated individually by simply calculating the difference between the value of one’s zakatable assets and one’s zakatable liabilities (explained later). This means that your shares are like other tradable goods and their Zakat value is what the market price of these shares is. It is important to note that Zakat date is to be determined according to lunar years. The Zakat date can be changed when a person goes totally bankrupt and is not Sahib-e-Nisab anymore. In this case, his Zakat date would be the date when he becomes Sahib-e-Nisab again.

Source: Pakistan Today April 18, 2021 10:52 UTC