When and how is Zakat calculated on shares purchased in an Islamic bank with the intention of selling them after several years, along with purchasing additional shares with the annual profit?

The shares you bought with the intention of reselling them are subject to zakat as trade goods if a hawl (full lunar year) has passed on the original capital with which you purchased them, and their value at the time of the hawl reaches the nisab (minimum threshold). Zakat is due on them every year, including their profits. The obligatory amount is two and a half percent (2.5%) of the capital and the profits generated from it.