I'll put in some sample numbers to better illustrate what I'm talking about. Creating a loss isn't an issue, it's getting no benefit from claiming RE tax on Sched E because of past carried over expenses.
Situation ignoring carryover Business use %age is 5/6ths (83.3%) Rent: $9000 Total RE tax: $6000, so $5000 business, $1000 personal Other current year expenses: $3000
So ignoring carryovers there is a $1000 profit:
$9000 (rent) ($5000) (business part of RE tax) ($3000) (other deductible expenses) ------- $1000
But in actuality there are carrovers -- $6000 of carried-in opex and $20000 of carried-in depreciation.
So in this situation $1000 of the carryover will be used up to bring the net income to zero:
$9000 (rent) ($5000) (business part of RE tax) ($3000) (other deductible expenses) ($1000) (carried-in expenses) ------- $ 0 and a $1000 Sched A RE tax deduction
And that's why there's no (current year) benefit from claiming the RE tax on Sched E. If it were not claimed then more of the carryover would be used, so you could still have $0 net rental income but be able to deduct all the RE tax (on sched A):
$9000 (rent) ($3000) (other deductible expenses) ($6000) (carried-in expenses) ------- $ 0 and a $6000 Sched A RE tax deduction
Obviously, on a current-year basis this leaves the taxpayer is a better-off position. Both approaches give zero net rental income, but the latter approach does so with a bigger Sched A deduction (with the tradeoff being that more of the carried-in expenses are used up).
Thus the question of whether or not it is permissible to forego claiming the business portion of the RE tax and taking it all as a Sched A itemized deduction instead.