Property tax bills that are based on 2017 assessments will be due this Sept. 30  and again on March 31, 2019. The bills are based on a percentage of property assessments. Here are the percentages, or rollbacks, by property class for the 2017 assessments: commercial, industrial and railroad properties were set by 2013 property tax legislation at 90 percent; multifamily properties, 78.75 percent; residential, 55.6 percent; and agriculture, 54.4 percent. According to the Polk County assessor’s office, there is $43 billion in taxable property in the county. Residential properties make up about $28 billion; commercial $9.8 billion; multifamily $1.5 billion; industrial $700 million; and farmland about $300 million. Of the total, $3.7 billion is exempt from property taxes.