How do you know if you have to get an inspection or not

If it's over 5 years old but not over 10 years old and has less than 150,000 miles you don't. if it's a purchase and has an out of state title you need an id/od inspection. If its older than 10 years or if its 5-10 years old with 150,000 or more miles and is even year vehicle in an even year you need inspection. Information is on dor.mo.gov

https://dor.mo.gov/motorv/help.php Here's where you look for accurate answers