Is zakat obligatory on a shared plot of land prepared for sale or rent, which has not yet been built upon? And is zakat calculated based on its old or new price? And is zakat obligatory on company shares, and how is it calculated?

Zakat (definition) is not obligatory on land unless it was intended for trade at the time of purchase, and the share of each owner reaches the nisab (definition) (minimum threshold) either by itself or by adding money or trade goods, and a full year (hawl) passes over it without changing the intention of trade. As for Zakat on shares: if the contribution is for the purpose of benefiting from profits without trading, then Zakat is obligatory only on the profit if it reaches the nisab and a full year passes over it. But if it is for the purpose of trading, then the shares themselves are subject to Zakat as trade goods, by evaluating their value and paying one-quarter of one-tenth (2.5%) of it at the end of each year.