Is Zakat on money obligatory on the total amount of money present, or only on the amount that has completed a full year (hawl)? And is it permissible to pay Zakat in monthly installments or to delay it until Ramadan to increase the reward?

Zakat is obligatory annually on wealth that reaches the nisab (minimum threshold) and on which a full year (hawl) has passed. If other wealth is added to it that is not profit generated from it, the owner has a choice: either to pay zakat on it at the time the zakat for the first wealth becomes due, or to pay zakat on it when a year has passed since it came into his possession.

It is not permissible to pay zakat in installments; rather, it must be paid in full immediately. It is also not permissible to delay it beyond its due month, even with the intention of paying it in Ramadan.