Is Zakat obligatory on housing allowance entitlements that were disbursed five years after returning from the scholarship, and is Zakat due for six years or for one year?

If the acquisition of wealth is not certain, such as a debt owed by an insolvent person, then there is no zakat (definition) on it until it is collected and a hawl (a full lunar year) passes over it. However, if the debtor is solvent and the debt can be recovered from him, then zakat is obligatory upon the creditor whenever a hawl passes, provided the debt itself reaches the nisab (definition) (minimum threshold for zakat) or reaches it when combined with other assets.