Q: Why are liabilities deductible?
A: Not all liabilities are deductible, only certain debts are deductible. Worship has not been enjoined to bring difficulty to man, rather, worship is there to accelerate man to Allah whilst considering his needs, circumstances and life. Thus, Ṣalāh has only been enjoined five times a day with most prayers in the evening when a person is free from the chores of the day. Ḥajj is only obligatory if a person can safely reach Makkah and bear all the costs. Fasting has been enjoined only for the day with strong encouragement in the Sunnah to eat right up to the break of dawn and to break the fast immediately upon sunset. In the same manner, a person who has wealth can first deduct his liabilities and debts from his total before determining how much wealth he must pay Zakat upon.
One of the reasons why Zakat is not due on life essentials such as food, shelter and clothes is that these items ward off harm from oneself. They are essentials to survive and they preserve life. The repayment of debt is also considered an essential of life; repayment of debts protect a person from punitive measures and legal action. Therefore, Zakat is not due on immediate debts just as Zakat is not due on other life essentials.
And Allah knows best!
Mufti Faraz Adam