"Just" seems to be doing a lot of work in that last sentence. I'm sure you know the idea behind vacancy taxes is to incentivize owners to offer rents that not only serve nominal purposes in making finance/accounting work but actually get takers so the space is productively used and mitigate any weird dynamics where there's simultaneously empty space there's no takers on and would-be renters who can't find anything they can afford, a situation which presents an apparent market failure.
If Spirit Halloween or whatever equivalent you're imagining is offered a rent they're willing to pay, then there is no market failure and policy is working.
How does that represent "getting around" the vacancy tax? Are we imagining that owners are creating Shell Game Seasonal Retail Inc™ and renting to themselves?
Spirit Halloween, small churches, etc all rent at far below market rates for various reasons, one of which would be "avoiding vacancy taxes". The key is they're always month-to-month and can be booted quickly if a "real" client shows up. I was with a smallish business that rented the other half of our building this way as temporary warehouse space, for something like 10% what we were paying for the warehouse space on "our side of the fence".
I think they could be structured in such a way as to at least help the situation, but they'd for certain be gamed.
If Spirit Halloween or whatever equivalent you're imagining is offered a rent they're willing to pay, then there is no market failure and policy is working.
How does that represent "getting around" the vacancy tax? Are we imagining that owners are creating Shell Game Seasonal Retail Inc™ and renting to themselves?