Is zakat obligatory on a sum of money that has reached the nisab and a hawl has passed while it is a debt owed by a trustworthy and committed friend, to be repaid in installments: Are the installments to be paid zakat on separately, or is the entire sum to be paid zakat on when all installments have been settled?

The preponderant opinion is that zakat on a debt is obligatory upon the creditor in all cases, whether the debtor is solvent or insolvent, willing to pay or procrastinating. It is obligatory to pay zakat on this money for every year. However, as long as the money is owed by an insolvent person, it is permissible to delay its zakat until it is collected, and then zakat is paid for all the past years, or for one year. As for what has been collected, zakat is paid immediately upon its collection.