Is Zakat obligatory on money that I lent and is still owed by the debtor?

If the amount paid is a loan, then it is not permissible to stipulate an increase on it, because that is usury (riba). However, if it is in the form of a partnership in trade (mudarabah), then it is permissible with a known share of the profit, and the loss is borne by the capital. It is not permissible to stipulate the full return of the amount if it perishes without negligence. The capital and its profit are subject to zakat after a year has passed, if it is a mudarabah.