The letter codes printed on a Missouri CDL are restriction codes, and each one narrows what commercial vehicles you’re allowed to drive. Missouri CDL restriction codes come partly from federal rules under the Federal Motor Carrier Safety Administration and partly from the state itself. They’re triggered by the vehicle you tested in, your age, or your medical status, and most of them can be removed by retesting or updating your paperwork.
What Each Restriction Code Means
L — No Air Brakes
An L restriction bars you from operating any commercial vehicle equipped with air brakes. You’ll get it if you fail the air brakes knowledge test, can’t identify air brake components during the pre-trip inspection, or take the skills test in a vehicle without air brakes. An L also prohibits driving vehicles with air-over-hydraulic brake systems.1Missouri Department of Revenue. Missouri Commercial Driver License Manual
Z — No Full Air Brakes
The Z code is narrower than the L. You receive it when you take the skills test in a vehicle with air-over-hydraulic brakes rather than full air brakes. With a Z, you can drive air-over-hydraulic systems, but nothing that runs entirely on air brakes.2eCFR. 49 CFR 383.95 – Restrictions in Lieu of Skills Tests
E — No Manual Transmission
Test in a truck with an automatic transmission and you’ll get an E, which prevents you from driving any commercial vehicle with a manual transmission. For this purpose, “automatic” covers any transmission that doesn’t operate fully on a clutch-and-gear-shift system.2eCFR. 49 CFR 383.95 – Restrictions in Lieu of Skills Tests This one catches more drivers than expected, because many newer training trucks use automated manual transmissions that qualify as automatic for testing purposes.
O — No Tractor-Trailer
An O bars you from driving tractor-trailer combinations connected by a fifth wheel. You get it when you pass the Class A skills test in a combination vehicle that uses a pintle hook or another non-fifth-wheel connection. Because most over-the-road trucking uses fifth-wheel setups, an O restriction significantly limits Class A job options.1Missouri Department of Revenue. Missouri Commercial Driver License Manual
M and N — Passenger Vehicle Limits
An M means you can’t operate a Class A passenger vehicle or school bus even if you hold a Class A CDL, because you tested in a Class B vehicle for the endorsement. An N goes further and limits you to Class C passenger vehicles and school buses only, because you tested in a Class C vehicle while holding a Class B CDL.3Federal Motor Carrier Safety Administration. Drivers
K — Intrastate Only
A K restriction confines your commercial driving to Missouri. You can’t cross state lines or engage in interstate commerce. K most commonly applies to drivers between 18 and 20, since federal law requires interstate commercial drivers to be at least 21. It also applies to drivers with certain medical conditions that satisfy Missouri’s intrastate standards but fall short of federal interstate physical requirements.1Missouri Department of Revenue. Missouri Commercial Driver License Manual
V — Medical Variance
A V appears when you hold a medical certificate along with a federal Skill Performance Evaluation (SPE) certificate or medical waiver. It applies to drivers with physical conditions such as missing limbs or impairments that would otherwise disqualify them. To earn the SPE certificate, the driver must be fitted with the appropriate prosthetic device if applicable and pass on-road and off-road driving activities showing they can safely handle the truck.4Federal Motor Carrier Safety Administration. Skill Performance Evaluation Certificate Program The V tells law enforcement and employers to look at the driver’s CDLIS record for the specific variance.5eCFR. 49 CFR 383.153 – Information on the CLP and CDL Documents and Driving Record
Missouri-Added Codes
Beyond the federal set, Missouri prints several state-specific codes:
- P (No Passengers in CMV Bus) is placed on commercial learner’s permits so the holder can practice driving a bus without carrying passengers. The only people allowed onboard are auditors, inspectors, test examiners, other trainees, and the CDL holder accompanying the permit holder.
- W (Farm Waiver) limits commercial driving to a specific 180-day period. Outside that window, the driver must operate non-commercial vehicles only.
- X (No Cargo in CMV Tank Vehicle) prevents the driver from hauling cargo in a tank vehicle.
- U194 restricts the driver to operating Class C school buses only.
- U195 restricts the driver to operating Class B or C school buses.
These codes are explained on the front or back of the CDL document, as federal rules require states to do whenever they add codes beyond the standard set.1Missouri Department of Revenue. Missouri Commercial Driver License Manual
Why the Code Ended Up on Your License
Most restrictions land on your CDL because of the vehicle you used at your Missouri State Highway Patrol skills test. If the truck had an automatic transmission, no air brakes, or a pintle hook instead of a fifth wheel, the corresponding code is added automatically. The examiner has no discretion. Federal regulations require it.
Age and medical factors work differently. A driver under 21 receives the K restriction by default regardless of the test vehicle. A medical examiner who identifies a disqualifying physical condition can send the driver toward a federal SPE certificate or medical waiver, which produces a V restriction rather than an outright denial. Vision problems or other conditions that don’t meet federal interstate standards but satisfy Missouri’s intrastate standards can also trigger a K, limiting the driver to in-state commerce.
How to Remove a CDL Restriction
Equipment-Based Restrictions: L, Z, E, and O
To drop an equipment restriction, you go back to a Highway Patrol examination station and demonstrate proficiency in the equipment you were originally restricted from. Removing an L requires passing the air brakes knowledge test and then completing a skills test in a vehicle with full air brakes. Removing an E means passing the skills test in a manual transmission vehicle. Removing an O means testing in a tractor-trailer combination with a fifth-wheel connection.1Missouri Department of Revenue. Missouri Commercial Driver License Manual
Each retest is the full skills evaluation: pre-trip inspection, basic vehicle control, and on-road driving. When you pass, you receive a skills test results form that documents the removal for your license upgrade.
K Restriction
A K lifts automatically once the underlying reason is gone. For drivers under 21, turning 21 is enough, though you still need to visit a license office to get the updated credential. For a medical-based K, you need to obtain a medical certificate that meets federal interstate standards.
V Restriction and Medical Certification Updates
Missouri overhauled its medical certification process in April 2025. The state now accepts electronic medical certificate data transmitted directly from the National Registry of Certified Medical Examiners, and drivers are no longer required to submit paper copies to the Department of Revenue. If you self-certify as non-excepted interstate or non-excepted intrastate, the Department pulls your medical examiner certificate information from the National Registry and posts it to your driving record. As of June 2025, drivers whose records reflect valid medical certification no longer need to carry the physical medical card while operating.6Missouri Department of Revenue. Commercial Driver License (CDL) Medical Certification FAQs
The electronic system does not automatically update records for drivers who self-certify as excepted interstate or excepted intrastate, drivers without a valid Missouri CDL or CLP, or drivers whose commercial credential has expired. Those drivers should contact the Department of Revenue directly to resolve their certification status.6Missouri Department of Revenue. Commercial Driver License (CDL) Medical Certification FAQs
Getting the Updated License Issued
After you pass the required tests or clear the medical hurdle, bring your skills test results form to any Missouri license office. You’ll pay the duplicate license fee, which for a Class A, B, or C license is $29 for a three-year term or $38 for a six-year term.7Missouri Department of Revenue. Missouri Driver License and Nondriver License The clerk issues a temporary paper permit on the spot, so you can start operating under the new authority immediately. Your permanent hard-card license arrives by mail within 7 to 10 business days. If it hasn’t shown up after 25 business days, contact the Department of Revenue to request a replacement at no additional cost.
If You Drive Outside a Restriction
Operating a commercial vehicle outside your restriction codes is treated the same as driving without a valid CDL for that vehicle. During a roadside inspection, a law enforcement officer or FMCSA inspector who finds you behind the wheel of a full-air-brake truck with an L restriction can place you out of service on the spot. The truck doesn’t move until a properly licensed driver takes over.
The problems don’t end at the roadside. The violation can surface in your carrier’s safety record during federal compliance reviews, which look at whether the motor carrier is using properly qualified drivers. Repeated driver qualification violations can trigger enforcement actions against the carrier, which gives employers strong reason to verify restriction codes before handing over the keys. For you, the citation goes on your driving record and can affect your employability in the industry long after the fine is paid.