Is zakat obligatory on a sum of money deposited in a bank for savings, from which withdrawals are made when needed, such that it does not increase?

You must repent for depositing money in interest-based banks, withdraw the money, and dispose of the profits by spending them on Muslim welfare or by giving them as charity to the poor. The principal amount is subject to Zakat if it reaches the threshold (nisab) on its own or when combined with other assets. As for Islamic banks, the principal amount and profits are subject to Zakat if their total reaches the nisab and a full year (hawl) has passed. The nisab for banknotes is the equivalent value of 85 grams of gold or 595 grams of silver, and the Zakat rate is one-quarter of one-tenth (2.5%).