You just bought a used car, or you are about to bid on one, and you live in the St. Louis area. Before Missouri will title or renew it, the car may need to pass an emissions test. Here is who needs one, what it costs, and how to keep a failed test from wrecking a good deal.
The short answer: If your car is registered in St. Louis City or St. Louis, St. Charles, or Jefferson County, it needs an emissions test when it changes title and every other year at renewal. The rule covers gas cars from 1996 on and diesels from 1997 on, up to 8,500 pounds. The test costs no more than $24 and is good for 60 days.
Updated October 7, 2026. Checked against the Missouri Department of Natural Resources Gateway Vehicle Inspection Program, the Missouri Department of Revenue, and the Illinois EPA. Sources are linked at the bottom.
Key takeaways
- Where: St. Louis City, St. Louis County, St. Charles County, and Jefferson County. Franklin County dropped out on July 1, 2022.
- When: any title transfer, plus every two years at renewal. Even model years test in even years, odd model years in odd years.
- Cost: up to $24 for emissions and up to $12 for a safety inspection, with one free retest at the same station within 20 business days.
- Shelf life: a passing test is good for 60 days for an owner, so test close to the day you title or renew.
- Auction buyers: Missouri’s dealer return rule does not cover cars bought at public auction, so check for emissions red flags before you bid.
Who needs an emissions test in St. Louis?
The test is part of the Gateway Vehicle Inspection Program, run by the Missouri Department of Natural Resources and the Missouri State Highway Patrol. Your car is in the program if all of these are true:
- Registered in the area: the car is registered in St. Louis City or in St. Louis, St. Charles, or Jefferson County. The state also tests cars that do at least 51% of their yearly miles in that area, no matter where they are registered.
- Right model year: a gas car from 1996 or newer, or a diesel from 1997 or newer.
- Right size: a gross vehicle weight rating of 8,500 pounds or less. That covers almost every car, SUV, minivan, and light pickup.
St. Louis City vs. St. Louis County vs. St. Charles County
| Where the car is registered | Emissions test? | Safety inspection? |
|---|---|---|
| St. Louis City | Yes | Only if the car is old or high mileage |
| St. Louis County | Yes | Only if the car is old or high mileage |
| St. Charles County | Yes | Only if the car is old or high mileage |
| Jefferson County | Yes | Only if the car is old or high mileage |
| Franklin County | No, since July 1, 2022 | Only if the car is old or high mileage |
| Illinois Metro East | Illinois runs its own program | Illinois rules apply |
Some websites still list Franklin County. That is out of date. The Department of Natural Resources says Franklin County vehicles stopped needing the test on July 1, 2022.
Which cars are exempt from emissions testing in Missouri?
The Gateway program lists these exemptions:
- Older cars: gas cars from 1995 and older, and diesels from 1996 and older. They may still need a safety inspection.
- Brand-new cars: new, unused vehicles with fewer than 6,000 miles at the original sale.
- Electric cars and plug-in hybrids.
- Motorcycles and motortricycles.
- Special plates and uses: historic vehicles registered under section 301.131 RSMo, specially constructed and kit vehicles, school buses, and tactical military vehicles.
- Low mileage: the program lists a low-mileage exemption for a two-year-old car under 40,000 miles, or a car four years or older driven fewer than 12,000 miles in the past two years. You need proof of the odometer readings.
Exemption and waiver forms are on the Gateway program’s forms, waivers, and extensions page.
How much does an emissions test cost in St. Louis?
State law caps the price. Stations can charge less, and they set which payment types they take.
| Item | What Missouri says |
|---|---|
| Emissions test | Up to $24 |
| Safety inspection | Up to $12 for a car or truck |
| Retest | One free retest at the same station within 20 business days |
| Wait time | The station must inspect your car within two hours of your arrival |
| Valid for | 60 days for an owner, 120 days for a dealer |
So the most you should pay for both inspections is $36. Find a licensed shop with the official Gateway station locator. Not every repair shop is licensed to test.
What happens during the test?
There is no tailpipe probe. The inspector plugs a computer into the OBDII port under the dash and reads the car’s emissions systems, including the catalytic converter, oxygen sensors, evaporative system, and exhaust gas recirculation. Any emissions trouble codes print on your inspection report.
Two things trip people up:
- Check engine light: if it is on, the state says the emissions system is not working right. The station tests the car as it arrives, so do not clear codes on the way in.
- Readiness monitors: a recently disconnected battery or cleared codes can leave the car’s self-checks unfinished. The program suggests driving 4 to 7 days of mixed city and highway miles before a retest.
Do you need an emissions test to transfer a title in Missouri?
Yes, if you live in the four-area region and the car is not exempt. The Department of Revenue requires an emissions inspection no more than 60 days old when you title. You have 30 days from the purchase date to title, or you pay a $25 penalty that grows by $25 every 30 days, up to $200.
Who pays for the test depends on how you bought the car:
| How you bought it | Who handles the test |
|---|---|
| Private seller | The seller must give you a current passing test or waiver before the sale. You then have 60 days from the test date to register. The state says this overrides an “as is” sale. |
| Missouri dealer | The dealer gives you a test from the last 120 days, or tells you in writing that you can return the car within 10 days and 1,000 miles if it fails, for a free repair. |
| Public auction | The dealer return rule does not apply. Neither does it for junk, salvage, or rebuilt titles. Plan on testing and fixing it yourself. |
A used car can need two tests in a row. The state’s example: a 2016 car bought in 2021 needed a test to title, then another in 2022 because it is an even model year. A 2019 car you buy in 2026 works the same way: one test to title now, then its regular test in 2027.
The full list of forms is in our Missouri title transfer guide, and the tax bill is broken down in Missouri car sales tax in St. Louis. If the two steps blur together, read car registration vs title transfer.
Do you also need a safety inspection?
Maybe. The Department of Revenue exempts a car for the first ten years after its model year if it has fewer than 150,000 miles. Older or higher-mileage cars need a safety inspection, which is valid for 60 days, or 90 days if you bought from a Missouri dealer. If the car has an out-of-state title, Missouri may also ask for an identification number and odometer inspection, and a current safety inspection covers that.
What if your car fails emissions?
- 1. Keep the report. You get a vehicle inspection report with the failed item, a list of the ten nearest Missouri Recognized Repair Technicians, and a repair data sheet.
- 2. Pick a shop. Anyone can fix the car. Labor only counts toward a cost-based waiver if a Missouri Recognized Repair Technician does the work.
- 3. Fix the code that failed. Repairs have to address the trouble code from the failed test.
- 4. Drive it. Give it several days of normal driving so the readiness monitors reset.
- 5. Retest at the same station within 20 business days to get the free retest.
- 6. Ask about a waiver if repairs do not get it to pass. You apply with the Department of Natural Resources.
One rule matters more than the rest: get the failing test before you repair anything. The state says repairs made before a test can cost you waiver eligibility.
Buying at auction? Check emissions before you bid
Auction cars are where emissions surprises cost the most, because nobody owes you a free repair. A few minutes of checking can save a few hundred dollars:
- Look at the dash photos: a lit check engine light is the biggest red flag for a St. Louis buyer.
- Read the condition report: notes about the catalytic converter, oxygen sensors, or exhaust leaks point to emissions work. Our car auction inspection tips cover what else to look for.
- Check the history: a vehicle history report can show past failed inspections or long gaps in registration.
- Budget for it: add the $24 test, a possible $12 safety inspection, and a repair cushion to your maximum bid.
- Watch the clock: you have 30 days to title, and the test has to be less than 60 days old when you do.
For where the public can bid locally, see our guide to car auctions in St. Louis, MO and the wider list of car auctions in Missouri. Shopping on a tight budget? Cars under $1,000 in St. Louis explains what to watch for, and cheap cars in St. Louis under $3,000 covers the next price tier. Cheap cars are the ones most likely to fail.
Live in the Illinois Metro East?
Missouri’s program does not apply to cars registered in Illinois. Illinois runs its own program, and the Illinois EPA says it covers the Metro East St. Louis area. It tests most 1996 and newer gas passenger cars and light trucks once they are four years old, on an odd and even model year schedule. Check your notice or the Illinois Air Team site to see if your car is due. More on buying across the river is in car auctions in Illinois.
Why St. Louis buyers bid on Remarket Space
Remarket Space is an online car marketplace open to the public. You do not need a dealer license or a membership. Every listing has an inspection report, a free Carfax, real photos, and an HD virtual test drive, so you can look for a check engine light and emissions notes before you bid, not after. Each listing also shows the out-the-door total with a delivery quote to St. Louis, and out-of-state buyers do not pay Minnesota DMV fees at checkout. Fee tiers are on our pricing and fees page.
See cars up for auction now, learn how bidding works, or browse cars under $5,000, cars under $10,000, and used sedans. Those pages list cars currently in Minnesota, and each one ships to St. Louis with a delivery quote. First time? Read how to buy a vehicle on Remarket Space.
Frequently asked questions
Yes. Gas cars from 1996 and newer and diesels from 1997 and newer, up to 8,500 pounds, registered in St. Louis County need an emissions test at every title transfer and every two years at renewal. St. Louis City, St. Charles County, and Jefferson County follow the same rules.
Missouri caps the emissions test at $24 and the safety inspection at $12, so the most you should pay for both is $36. The fee includes one free retest at the same station if you return within 20 business days.
A passing emissions test is valid for 60 days for a vehicle owner and 120 days for a car dealer. If you do not title or renew within that window, the car has to be tested again, so plan the test close to your license office visit.
New, unused vehicles with fewer than 6,000 miles at the original sale are exempt. The program also lists a low-mileage exemption for newer cars, plus exemptions for electric cars, plug-in hybrids, and motorcycles. A used car changing hands usually needs a test.
Only in St. Louis City and St. Louis, St. Charles, and Jefferson counties, and only every other year. Even model year cars test in even years and odd model year cars test in odd years. Your renewal notice arrives about 60 days before the plates expire.
No. Vehicles registered in Franklin County have not needed an emissions test since July 1, 2022. They may still need a safety inspection if they are more than ten years past their model year or have 150,000 miles or more.
Keep the failing report, have the trouble code repaired, drive the car for several days, and return to the same station within 20 business days for a free retest. If repairs do not work, you can apply to the Department of Natural Resources for a waiver.
Sources
- Gateway Vehicle Inspection Program: Do I need to test?
- Gateway Vehicle Inspection Program: Cost of testing
- Gateway Vehicle Inspection Program: Vehicle failed emissions test
- Gateway Vehicle Inspection Program: Vehicle sales and title transfers
- Missouri Department of Natural Resources: Gateway Vehicle Inspection Program FAQ
- Revised Statutes of Missouri 643.315: Emissions inspection requirements
- Missouri Department of Revenue: Buying a vehicle
- Missouri Department of Revenue: Safety and emissions inspection requirements
- Missouri State Highway Patrol: Motor vehicle inspection FAQ
- Illinois EPA: Vehicle inspection program update
This guide is general information, not legal advice. Rules and fees can change, so confirm with the Missouri Department of Natural Resources or Department of Revenue before you title or renew.
