Is Zakat obligatory on a plot of land that a person owns and does not intend to sell currently, but plans to build a house on it in the future for investment?

There is no zakat on land unless its owner intends it for trade. If it is built upon and invested in, then zakat is due on the money earned from it, provided it reaches the nisab (threshold) and a hawl (one lunar year) passes over it. There is no zakat on land intended for dwelling or exploitation; rather, zakat is due on the rent earned from it if a hawl passes over it. The land on which zakat is due is that which a person has prepared for sale and earning profit, but that which he has prepared for his needs or for his own use has no zakat on it.