I never received a bill, so why should I have to pay the tax?

You will not be excused from paying the tax or penalty because you failed to receive a tax bill.  Registration of a motor vehicle places you on notice that a tax will be assessed.  If you do not receive a bill for the tax year you have a duty to inquire with the tax collector.  "Failure of the tax collector to send or by taxpayer to receive a bill shall not excuse the non-payment of tax or affect its validity of any proceeding for the collection thereof."  R. I. Gen. Laws §44-34-3(e).

All motor vehicles registered in your name will be taxed each year by the city or town listed by you with the Registry of Motor Vehicles at which the vehicle will be kept.  This tax is referred to as the Motor Vehicle Excise Tax and that tax is assessed in accordance with Title 44, Chapter 34 of the General Laws of the State of Rhode Island.