Written by the America’s Driving Force team · Reviewed by Joel Curtis, retired professional truck driver · Published September 29, 2026 · Last reviewed September 29, 2026 · Sources are listed at the end
CDL endorsements add permission to drive specialized vehicles. Federal rules use the letters T for doubles and triples, P for passenger, N for tank, H for hazardous materials, X for tank plus hazmat, and S for school bus. Passenger and school bus also need a skills test, and the hazmat endorsement requires a TSA security check.
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What an endorsement is
A CDL class tells you what size and type of vehicle you may drive. An endorsement adds permission to drive specialized vehicles or carry special loads. The federal rule on endorsements, 49 CFR 383.93, says that anyone who operates or expects to operate the vehicles it describes must pass specialized tests, on top of the regular knowledge and skills tests, to earn each endorsement. The state issues an endorsement only to drivers who pass those tests.
Under the regulation, you need a state-issued endorsement to operate commercial motor vehicles that are double or triple trailers, passenger vehicles, tank vehicles, vehicles used to transport hazardous materials as defined in the rules, or school buses.
Endorsement letters and the tests they require
The letters printed on a CDL come from 49 CFR 383.153. Combined with the testing requirements in 383.93, here is how they fit together:
| Letter | Endorsement | Tests required |
|---|---|---|
| T | Double/triple trailers | Knowledge test |
| P | Passenger | Knowledge test and skills test |
| N | Tank vehicle | Knowledge test |
| H | Hazardous materials | Knowledge test |
| X | Combination of tank vehicle and hazardous materials | Both the tank vehicle and hazardous materials requirements |
| S | School bus | Knowledge test and skills test |
The regulation lets states add discretionary codes for additional groupings of endorsements, as long as each is explained on the license. Note that the X code is a printed combination of N and H, not a separate test in the 383.93 list.
Which endorsements you can hold on a learner's permit
Some endorsements can be earned while you still hold a learner’s permit, but with limits. According to 49 CFR 383.25 and 383.93, the only endorsements allowed on a commercial learner’s permit are passenger (P), school bus (S) and tank vehicle (N). The permit rules add the following:
- A permit holder with a P endorsement may not operate a commercial vehicle carrying passengers, other than certain auditors, inspectors, test examiners, other trainees and the accompanying CDL holder.
- A permit holder with an S endorsement may not operate a school bus with passengers, apart from the same exceptions.
- A permit holder with an N endorsement may only operate an empty tank vehicle, and may not operate any tank vehicle that previously held hazardous materials and has not been purged of residue.
- All other federal endorsements are prohibited on a permit, and a permit holder may not operate a commercial vehicle transporting hazardous materials.
In other words, the T and H endorsements are earned on the CDL itself, not on the permit.
Training rules for P, S and H endorsements
Federal entry-level driver training rules apply to three endorsements. Per the Training Provider Registry’s frequently asked questions, first-time applicants for the passenger and school bus endorsements need theory training plus behind-the-wheel training on the range or public road, verified before the skills test. First-time hazardous materials applicants need theory training only, verified before the knowledge test. Endorsements T and N are not part of that federal training requirement in the registry’s summary. We explain who must complete the training in a separate guide on entry-level driver training.
The registry FAQ also notes that states can add their own conditions. For example, a state may require an additional state certification for school bus drivers on top of the federal requirements, so check your state’s CDL manual for the full list before you apply.
The TSA check for the hazmat endorsement
The hazardous materials endorsement is the only one that involves a federal security check. The Transportation Security Administration’s HAZMAT endorsement page says its Security Threat Assessment applies to any driver seeking to obtain, renew or transfer a hazardous materials endorsement on a state-issued CDL, and that you should apply if you must transport materials that require placarding under the Department of Transportation’s hazardous materials regulations. As read on September 29, 2026, the page says:
- You can pre-enroll online or complete the process in person at an enrollment center, except in Florida, Kentucky, Maryland, New York, Pennsylvania, Texas, Virginia and Wisconsin, where applicants should contact the local motor vehicle office for application and fingerprinting information.
- At an enrollment center you provide documentation and fingerprints and pay a non-refundable fee that is valid for five years. The listed fee is $85.25 for new and renewing applicants, or $41.00 at a reduced rate for people who already hold a valid TWIC card and are licensed in a state that accepts the TWIC assessment.
- TSA recommends enrolling at least 60 days before you need an eligibility determination, and warns that processing may exceed 45 days for some applicants.
- Eligibility is open to U.S. citizens, lawful permanent residents, naturalized citizens and certain nonimmigrants, asylees or refugees in lawful status who hold a CDL issued by a U.S. state. Applicants may be ineligible because of incomplete or false information or disqualifying criminal offenses. TSA says to check with your state for stricter citizenship or lawful presence requirements.
Fees, timing and procedures can change, so confirm the current details on TSA’s page and with your state.
Choosing endorsements for the work you want
The right endorsement depends on the work you want. Drivers who pull double or triple trailers need T. Passenger and school bus work needs P or S, which also require a skills test. Tank truck drivers need N, and a driver who hauls placarded hazardous materials needs H, or X if the truck is also a tank vehicle. Ask a prospective employer which endorsements the job requires before you spend money on tests.
To see what carriers in your state haul, browse our directory of trucking companies in all 50 states, which lists hazmat carriers on each state page. For the license classes these endorsements sit on, read our guide on Class A vs Class B CDL licenses.
Frequently asked questions
What does the X endorsement mean?
X is the code printed on a CDL for a combination of the tank vehicle and hazardous materials endorsements, per 49 CFR 383.153.
Which endorsements need a skills test?
Under 49 CFR 383.93, the passenger and school bus endorsements need a knowledge test and a skills test. Double/triple trailers, tank vehicle and hazardous materials need a knowledge test.
Which endorsements can I have on a learner's permit?
Only passenger (P), school bus (S) and tank vehicle (N), and each comes with restrictions on what the permit holder may drive.
Does the hazmat endorsement require a background check?
Yes. TSA says drivers seeking to obtain, renew or transfer a hazmat endorsement undergo a Security Threat Assessment. Check TSA's page for current fees and timing.
Does the hazmat endorsement need behind-the-wheel training?
The Training Provider Registry lists theory training only for a first-time hazmat endorsement, with no behind-the-wheel training.
Related guides
- Class A vs Class B CDL licenses compared
- Trucking companies in all 50 states
- Learning the basics of CDL training: classifications of a commercial driver's license
About the reviewer
Joel Curtis is a retired professional truck driver with more than 30 years of over-the-road experience in Canada and the United States. He reviews our guides for practical accuracy from a driver’s point of view. Every guide is built from the official sources listed below.
Sources
- 49 CFR 383.93 Endorsements, Electronic Code of Federal Regulations
- 49 CFR 383.153 Information on the CLP and CDL documents and applications, Electronic Code of Federal Regulations
- 49 CFR 383.25 Commercial learner's permit (CLP), Electronic Code of Federal Regulations
- HAZMAT Endorsement, Transportation Security Administration
- Frequently Asked Questions: Training Requirements and Curricula, FMCSA Training Provider Registry
This guide is general information, not legal or financial advice. Rules, fees and requirements change, so confirm current details with the agencies listed above and your state before you act.