Ruling 1900
Based on obligatory precaution, a person cannot deduct the expenses he incurs from the produce before or after zakat has become due and give zakat on only what remains.
-Ayatullah Sistani, Practical Laws of Islam, Alms Tax (Zakat)
Alms Tax: Deducting Expenses Before or After Zakat Becomes Due
Practical Laws of Islam as per the teachings of Ayatullah Sistani
