If you are an interstate motor carrier and have motorized commercial vehicles that cross state lines, you must register and pay the Uniform Carrier Registration Fee.  The fee is based upon the number of vehicles that operate in interstate commerce.  To register, go to https://icc.illinois.gov/motorcarrier/ucr.aspx  This website also has a handbook you can download that explains the UCR.  Enforcement will begin on April 1, so please be sure your UCR registration is current.