What is the ruling on Zakat for a debt owed by an insolvent person, a debt owed by a wealthy procrastinator, and a debt owed by a solvent debtor who intends to pay after the passage of a year?

If the debtor is insolvent or procrastinates and the creditor cannot collect his debt, then zakat is not obligatory for the creditor until he collects his debt and a hawl (full year) passes over it. However, if the debtor is solvent and the debt can be collected from him, then zakat is obligatory for the creditor whenever a hawl passes, provided that the debt reaches the nisab (minimum threshold) by itself or by combining it with other assets.