Is zakat obligatory on a sum of money that decreases monthly, given that I have no other source of income? Is expiation due for delaying its payment? And how is its zakat calculated if it is obligatory?

Zakat becomes obligatory on wealth when it reaches the nisab (minimum threshold) and a full lunar year passes over it, whether the owner is employed or not.

The nisab is equivalent to 85 grams of gold or 595 grams of silver, and the amount of Zakat is one-quarter of a tenth (2.5%).

Zakat must be paid immediately upon its due date. It is not permissible to delay it, as delay does not waive it; rather, it remains a debt upon one's conscience.

The need for money is not an excuse to forgo paying Zakat.

It is advisable to invest wealth in an Islamic bank or a growing project so that Zakat does not deplete it.