Is zakat due on the money a mother saved for her children, and if so, who is responsible for paying it, and is it permissible to pay it in installments after the money runs out?

It is obligatory upon minors, when they reach maturity, to pay zakat (definition) on the savings accumulated over all previous years, because zakat is not forfeited by the passage of time, and it is the right of the poor. It is permissible to postpone its payment or pay it in installments if one is unable to pay it in a lump sum. The guardian of an underage orphan's wealth must pay the zakat on the orphan's money without delay, because it is an obligation related to the wealth, not to the orphan.