Is Zakat obligatory on money saved for Hajj, which has reached the nisab and on which a full year has passed, taking into account the fluctuation of the amount by increase and decrease, and is Zakat calculated on the currently available amount or on the first installment?

Zakat is obligatory on money saved for Hajj if it reaches the nisab (minimum threshold) and a hawl (one lunar year) passes over it.

As for money acquired later, you have two options regarding its zakat: 1. To assign an independent hawl for each saved amount. 2. Which is easier and more beneficial for the poor: to pay zakat on all the saved money when the hawl passes on the first nisab you possessed. For example, if the hawl passes on the first nisab in Ramadan, you would pay zakat on all the money you saved in the following Ramadan.

The amount of zakat is a quarter of a tenth (2.5%) of the saved money that has reached the nisab. The nisab is equivalent to 85 grams of gold or 595 grams of silver, and the nisab is estimated based on what is more beneficial for the poor.