New Jersey gave Uber a $54 million bill back in 2015, but it's not certain if the company ever paid that.

Not surprisingly, Uber is contesting the bill. It told Engadget it was "challenging this preliminary but incorrect determination," insisting that drivers are "independent contractors." The company believes the bill overestimate its business in the state and that the process is still early. Uber has previously claimed that treating drivers as employees would limit their flexibility to work when they like, but critics have argued that this lets Uber avoid minimum wage and other labor guarantees.

Uber may face an uphill battle, though. Like other states, New Jersey has a test to determine if people are contractors, and it believes they are -- it doesn't buy Uber's claim that the ridesharing platform, not transportation, is its main business. So long as the state maintains that view, it'll continue to demand back taxes and might take legal action if Uber still refuses to pay.