How is zakat calculated on goods sold on credit if their price has not yet been collected?

If you sell goods on credit and have not received their price, and the debtor is able and acknowledges the debt, then you add the debt to your trade and pay zakat on the total amount when a complete year (hawl) has passed. However, if the debtor is insolvent, you are not obligated to pay zakat until you collect the debt.

As for debts you owe because you purchased goods but have not paid their price, you should deduct these debts from the wealth on which you intend to pay zakat.