Is Zakat obligatory on borrowed money?

If the debtor is wealthy and acknowledges the debt, zakat is obligatory on the lent money, because it is in the status of a deposit. However, if the debtor is insolvent, denies the debt, or procrastinates, zakat is not obligatory until the money is received. Once received, zakat is paid for one year, even if it remained with the debtor for many years.