City zoning can be taxing, and one Bronx pol is about to find that out the hard way.

Democratic State Sen. Jeffrey Klein’s law firm, on a residential street in Morris Park, has run afoul of zoning codes and will now have to pay thousands more in property taxes, the city said.

After a Post inquiry last week, the Finance Department looked into whether Klein’s firm was being taxed at the appropriate level, and found it wasn’t.

So the Finance Department will reclassify the building as a commercial property. Its former residential classification carries a lower tax rate.

mgartland@nypost.com