Thank you for the explanation. I don't know anything about reciprocity agreements, but it seems hard to imagine that I would have  to apply for an employer identification number in another state just because a seasonal employee happens to have an address there. So there should certainly be a way to specify that an employee's address is simply the permanent mailing address for payroll-related mail.

It feels not just "messy" to enter dummy numbers into QB, but also potentially legally worrisome, since I use QB directly connects with tax agencies for e-filing.