The State of Wisconsin Department of Revenue states:
"No. You may use only the portion of the property taxes that is allocable to the portion of the duplex that is your principal residence. For example, if both halves of the duplex are of equal size, you may use one-half of the property taxes paid on the duplex during the year for the [property] credit."
This statement aligns with claiming a property tax deduction for a duplex that is both personal and rental property. Generally, because the property tax covers two properties each property is entitled to deduct half of the tax.
However, any other expenses (e.g., advertising, management fees, repairs) related to the rented duplex can be written off in their entirety on the Schedule E.
