Alms Tax: Doubt Regarding the Sufficiency of Yearly Expenses
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1942
If a person has sufficient means to meet his expenses for a year and spends part of it, and then he doubts whether or not the remaining amount will be sufficient to meet his expenses for one year, he cannot receive zakat.
-Ayatullah Sistani, Practical Laws of Islam, Alms Tax (Zakat)