Is zakat obligatory on the principal amount gained from stock market investments if these investments are unlawful, knowing that the father provides for the questioner?

Purchasing shares in banks or other entities is conditional upon their activities being permissible and their funds not being invested in usurious ways. If a bank deals with usury—such as purchasing treasury bills—it is not permissible to buy its shares. The contract must be فسخ (dissolved), and the unlawful profits disposed of by spending them on charitable causes. As for the zakat on permissible shares, it is obligatory according to the rulings on zakat for shares. If the shares are impermissible and cannot be returned, zakat is obligatory on the original capital if a year has passed and it reaches the nisab. The profits are to be disposed of by spending them on charitable causes.