How is the zakah on a share in land of unknown value paid?

Question : The questioner says: I have a share in a piece of land from five years ago, and I do not know what it is worth at the present time, because it is not in my possession. How is the zakah paid?

Answer : It is obligatory for this man and others like him who have shares in lands or companies or other things to ask the officials who manage these shares every year, saying, "What is the value of the share?" and then to pay the zakah. For example, if he invested in a piece of land that the partners bought for one million riyals, and when the zakah became due it was worth one million.
This means the person pays zakah on what? Not on his partner’s share, nor on the entire million, for it is not all his. He pays zakah on double what he gave. For example, if he invested one hundred, he pays zakah on two hundred, because the land gained half its value. If the situation is the opposite, and he invested in land worth two million and actually paid the price, but when the zakah became due it was worth only one million, how much does he pay? Yes, he pays zakah on half his share, only half his share, because the land’s value dropped in the second year. He does the same in the third, the fourth, and the fifth year. Every year he asks the officials of this company what the value is and pays the zakah. Yes.