What is the ruling on zakat for money owed by a person who may not repay it, and does zakat remain due on it, and how can the zakat due date be changed to coincide with the month of Ramadan?

Purifying the salary (giving zakat on it) is obligatory according to Fatwa No. 32068. Zakat is also obligatory on loaned money unless the debtor is in hardship or procrastinating, in which case zakat is obligatory for one year after its recovery. It is not a condition to give zakat in Ramadan, but it is preferable. It is permissible to pay it in advance at the beginning of Ramadan before the zakat year (hawl) is complete, with the obligation to pay zakat on any additional growth the money accrues after the advance payment. It is not permissible to delay zakat beyond its due time.