Temp tags are only good for 30 days in MO. It will cost you $25 for each month after that. Even if it's 1-3 days late.
Getting plates in Mo is a pain the butt. I just moved here from Ohio and registered A car and two motorcycles. First you need to go to the county tax assessor and get a form. Without it you will not be able to register your car. Next you will need the title or a memorandum title to prove you own the vehicle. Next you will need an inspection which you need to pay for, around 20 bucks. Finally proof of insurance. I have lived in many states and have never had to jump through so many hoops to register a vehicle
No legal 'grace period' it's best to not drive it until you can get it legal. If you get pulled over it is up to the officer to give you a warning or a ticket.
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