How is the Zakat calculated on an installment-based sum of money that was borrowed for five years?

The preponderant view is that the lender is obligated to pay zakat on a debt in all circumstances. However, zakat is not due until the debt is collected. When collected, its owner pays zakat for the past years, or pays its zakat along with the zakat of his other wealth if the debtor is solvent and willing to pay. If the debtor is a procrastinator or insolvent, zakat is not due until after collection for the past years. Some scholars said zakat is due for only one year after collection, while others said a new hawl (lunar year) should begin for it. Therefore, the questioner should pay zakat on each installment he collects for the past years.