What is the amount of zakat that must be paid for the wife and family, taking into account owning a private residence, three cars, an import and export company and office that are out of business, an unprofitable restaurant, large debts to the bank, a growing retirement salary, and the questioner being responsible for supporting his wife, three university students, and other students?

There is no zakat (definition) on a person's residence, car, or real estate not intended for sale, nor on a travel and tourism company or an import-export office per se. Rather, zakat is due on the monetary income generated from them if a year has passed and it reaches the nisab (definition).

Similarly, there is no zakat on the owned share of a restaurant except for the monetary returns and the food and drink prepared for sale if a year has passed and it reaches the nisab. Fixed equipment not intended for sale is not included in the zakatable assets.

If a person has debts, these debts are calculated and offset against non-zakatable assets (such as surplus real estate, non-essential cars, and work equipment). If these assets cover the debt, all zakatable wealth is subject to zakat without deduction. If the debt is greater than the value of these assets, the excess is deducted from the zakatable wealth, and the remainder is subject to zakat.

A man is not obligated to pay zakat on his wife's wealth, but only on his own wealth.