If tenant has failed to pay and waiting on Rental Assistance

So ... you just have less rent to report on the Sch E.  

You still get to deduct all your expenses and claim a loss (or carry forward the loss, depending on your total income).  And when the tenant finally pays you, you will report the income in the year you receive it, not the year it shoulda been paid. 

Rental income is reported in the tax year you receive it. Doesn't matter what tax year that rent may be "for" either. You do not report income that you do not receive.