Is zakat obligatory on the value of a bank guarantee letter issued by the bank from the zakat payer's account in the form of certificates, from which he receives monthly profits?

Zakat (definition) is obligatory on the amount placed as collateral for a letter of guarantee because it is considered to be like mortgaged property, which is owned wealth that reaches the nisab (definition). Zakat becomes due on it if it is a Zakatable asset. As for how its Zakat is calculated: if the money is in an Islamic bank that invests it in a Sharia (definition)-compliant manner, then Zakat is due on the principal and its profit. If the money is in an interest-based bank, then Zakat is due only on the principal, while the profit is illicit wealth that must be disposed of. The certificates must be canceled, and the money placed in a current account until the need for the letter of guarantee ends.