Is it obligatory for someone who has paid their Zakat in advance to calculate their wealth again at the end of the year to ensure their obligation has been fulfilled?

There is no objection to expediting Zakat (definition), even for two years, according to the preponderant opinion. The method of expediting it is to pay Zakat on the existing wealth for two years. Then, at the end of each year, the wealth is reviewed; if it has increased, Zakat becomes due on the increase.

Regarding Zakat on salary savings, there are two methods: 1. The first (which is the easiest and most beneficial for the poor): Designating a day for the beginning of the Hawl (Zakat year) upon possessing the Nisab (definition) (minimum taxable amount). Then, on the same day of the following year, one-quarter of a tenth (2.5%) is paid on all savings, regardless of what has completed its Hawl and what has not. 2. The second: Establishing a separate Hawl for each amount saved monthly after it reaches the Nisab. This method is more difficult.

Any increase occurring after the payment of Zakat from the salary does not necessitate a review because it is not a result of the wealth on which Zakat was paid, unlike what a business owner or livestock owner would need to do.