unpaid housing allowance due to pastor

What if the Church was unable to pay the pastor 100% of the (actual amount spent by the pastor, (for housing allowance expenses allowed by the IRS)for that calendar year?

Can the Church write in their minutes that (the Church owes the pastor for unpaid housing allowance) and will pay the pastor the amount owed, the following year/s if the monies are available?

Can the pastor which has met the requirements for housing allowance and has been paid 100% for actual monies spent on housing expenses allowed by the IRS for the calendar year, receive the housing allowance owed to him? Would the excess be considered taxable income?

If the amount paid to the pastor (monies owed for unpaid housing allowance from previous year)does not exceed the current calendar year housing allowance allowed is this money considered housing allowance and not taxable income?