State police and the Department of Taxation and Finance say commercial motor carriers must register vehicles with the department and display the stickers on front bumpers.
That requirement took effect Jan. 1. It applies to vehicles with a gross weight of more than 18,000 pounds, except for trucks transporting automotive fuel.
Also excluded are buses and government and highway construction vehicles.
Citations can result in fines ranging from $100 to $250 for a first offense.
Tax officials cite more than 54,000 registrations so far, mostly online, resulting in collections of $3.5 million in outstanding taxes.
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