How is zakat to be paid on inherited money, knowing that a year has passed and financial changes have occurred, while the nisab remains?

Inherited wealth on which zakat is not obligatory, such as real estate and movable assets not intended for trade, carries no zakat. If it consists of trade goods, the majority of scholars hold that no zakat is due on them. However, some scholars mandate zakat on them if they are intended for trade, amounting to a quarter of a tenth of their value upon the completion of a year from the time of that intention.

If the inherited wealth is of a type on which zakat is obligatory, such as cash, then zakat becomes due upon the completion of a year from the time it came into your possession, provided it reaches the nisab (minimum threshold) either by itself or by combining it with other cash you possess. Whatever you spend during the year is not subject to zakat.

As for newly acquired wealth (that which you gain during the year): if it is a growth of the principal, such as trade profit, then zakat is paid when the principal's year is completed. If you acquired it through another means, such as a gift or salary, the majority of scholars hold that you calculate a separate year for each installment. However, paying zakat on all of it when the principal's year is completed is good and permissible according to the majority.