The vehicle is not to be used on Iowa roadways. Penalties will be applied. If you have credit from a vehicle you sold, you will still be able to get that credit as long as it is within six months from date of sale of that vehicle.
Story County Treasurer's Office highly suggests that you do not wait until the last day to transfer the vehicle. If additional information is needed and you are sent away penalty will still begin 30 days after the date of sale.