What is the method for paying Zakat on business assets for which Zakat has not been paid for years, and on surplus funds in the bank from which the son's education is financed, and on rented and unrented offices, and on the car and the house?

Zakat (definition) is a great pillar and a sublime ritual. Withholding it carries grave danger and leads to the loss of blessings. This has been affirmed in an authentic Hadith (definition) from the Prophet, peace and blessings be upon him. Therefore, the questioner must repent and pay the Zakat for his business for the past years during which he did not pay Zakat. He should review his accounts at the end of each year and pay Zakat on whatever reached the nisab (definition). Business Zakat is calculated by tallying cash and evaluating goods, then paying one-quarter of one-tenth (2.5%) of their total value. Debts owed by a solvent and willing debtor are subject to Zakat along with business assets. As for debts owed by an insolvent or procrastinating debtor, Zakat is paid on them only when they are collected. Funds saved in the bank are also subject to Zakat, and spending a portion of them on one's child does not negate their Zakat obligation. Rented and unrented offices, cars, private homes, household items, and business equipment not intended for sale are not subject to Zakat. However, the rent collected from shops, houses, or cars is added to one's wealth and Zakat becomes due on it.