Is Zakat obligatory on shares of an Islamic company under establishment that have not been offered for trading and the current share value is unknown?

Zakat is obligatory on the money you invested in the company if it reaches the nisab (minimum threshold) by itself or when combined with other wealth you own, whether it be cash or trade goods. Zakat is not obligatory until a hawl (one lunar year) has passed over the money, unless it is growth from existing wealth, in which case its hawl is that of its origin.