A, B or C identifies the vehicle group by weight, configuration or passenger/HazMat use.
Independent CDL & ELDT Information PortalOfficial FMCSA Registry ↗
CDL AUTHORITY GUIDE
CDL endorsements.
Know what each unlocks.
An endorsement adds authority to operate a specific type of commercial vehicle or carry a regulated load. Use this federal-baseline guide to understand who needs H, N, P, S, T or X—and exactly which training, knowledge, skills or security steps apply.
COMMERCIAL DRIVER LICENSE
AUTHORIZED OPERATIONSH · N · P
S · T · X
S · T · X
Class + endorsement + restrictionsAll three must match the vehicle and operation.
Hazardous MaterialsPlacarded hazardous materials
NTank VehicleLarge liquid or gas tanks
PPassengerBuses and passenger CMVs
SSchool BusSchool transportation
TDouble / Triple TrailersMultiple-trailer combinations
Tank + HazMatCombined N and H authority
THE FEDERAL BASELINE
An endorsement is not a CDL class.
H, N, P, S, T or X authorizes a specialized vehicle or operation after required testing.
A restriction limits equipment or operations—for example air brakes, manual transmission or passenger vehicle type.
01
HCDL ENDORSEMENTHazardous Materials
Drivers operating a CMV used to transport material that must be placarded under 49 CFR part 172, or any quantity of a listed select agent or toxin.
TESTINGKnowledge test + TSA screening
ELDTRequired for first-time H
Who commonly needs it
- Placarded chemical or fuel loads
- Explosives, gases and regulated dangerous goods
- Certain waste, radioactive or infectious materials
- Any CMV carrying a regulated select agent or toxin
Federal-baseline requirements
- 1Hold or qualify for the appropriate CDL class
- 2Complete HazMat ELDT theory with an FMCSA Training Provider Registry provider before the first H knowledge test
- 3Pass the state HazMat knowledge test
- 4Complete TSA's fingerprint-based Security Threat Assessment
- 5Meet federal immigration-status and security-eligibility rules
- 6Renew or transfer the HME under state and TSA procedures
What the test or training covers
Hazardous Materials Table and shipping papersMarking, labels, placards and packagingLoading, segregation, parking and routingTunnels, railroad crossings and safe havensEmergency equipment, incident reporting and response
Important distinctionH is not permitted on a CLP. A driver may not transport a load requiring H authority until the endorsement is issued.
02
NCDL ENDORSEMENTTank Vehicle
Drivers of a CMV designed to transport liquid or gaseous material in attached tanks when any individual tank exceeds 119 gallons and the aggregate rated capacity is at least 1,000 gallons.
TESTINGKnowledge test
ELDTFederal ELDT not required for N alone
Who commonly needs it
- Fuel and liquid cargo tank vehicles
- Food-grade liquid tankers
- Dry-bulk tank vehicles when the tank definition applies
- Temporarily attached qualifying tanks, including certain intermediate bulk containers
Federal-baseline requirements
- 1Hold or qualify for the CDL class matching the vehicle
- 2Pass the state Tank Vehicle knowledge test
- 3Understand surge, center of gravity and rollover risk
- 4Confirm whether the actual tanks meet both federal capacity thresholds
- 5Follow any additional state licensing steps
What the test or training covers
Cargo surge and vehicle handlingBraking when empty, full or partially fullBaffled, compartmented and smooth-bore tanksTank construction and product densityGrades, curves, emergency systems, retest and marking rules
Important distinctionA non-transport storage container of 1,000 gallons or more temporarily attached to a flatbed is excluded when it was not designed for transportation.
03
PCDL ENDORSEMENTPassenger
Drivers operating a CMV designed to transport 16 or more people, including the driver. The endorsement can apply to Class A, B or C depending on the vehicle group.
TESTINGKnowledge + skills tests
ELDTTheory + BTW required for first-time P
Who commonly needs it
- Transit and city buses
- Motorcoaches and charter buses
- Large shuttle and paratransit vehicles
- Passenger vehicles meeting the federal CMV definition
Federal-baseline requirements
- 1Obtain the appropriate CLP with P endorsement for supervised practice
- 2Complete P endorsement theory and behind-the-wheel ELDT with a listed provider before the first P skills test
- 3Pass the Passenger knowledge test
- 4Pass the CDL skills test in a representative passenger vehicle
- 5Meet the CDL class, medical and state application requirements
What the test or training covers
Safe passenger loading and unloadingEmergency exits and push-out windowsFire, evacuation and unruly-passenger responseRailroad crossings and drawbridgesPassenger-vehicle braking and operating procedures
Important distinctionThe class or restrictions on the resulting CDL depend on the passenger vehicle used for the skills test. Use equipment matching the work you intend to perform.
04
SCDL ENDORSEMENTSchool Bus
Drivers of a CMV used to transport pre-primary, primary or secondary students between home and school or to and from school-sponsored events.
TESTINGKnowledge + skills tests; P also required
ELDTTheory + BTW required for first-time S
Who commonly needs it
- Full-size school buses
- School activity buses when the federal definition applies
- Small school buses that qualify as CMVs
- District or contractor-operated pupil transportation
Federal-baseline requirements
- 1Qualify for the Passenger (P) endorsement
- 2Complete S endorsement theory and behind-the-wheel ELDT with a listed provider before the first S skills test
- 3Pass the School Bus knowledge test
- 4Pass the Passenger knowledge and skills requirements
- 5Take the skills test in a school bus of the same vehicle group you plan to drive
- 6Meet separate state, district and employer screening rules
What the test or training covers
Loading and unloading childrenStop arms, mirrors, flashing lights and warning systemsEmergency exits and student evacuationRailroad-highway grade crossingsSchool-bus operating practices and procedures
Important distinctionFederal rules exclude for-hire motor-carrier operations from the school-bus definition. States and employers may impose additional age, background, medical or training requirements.
05
TCDL ENDORSEMENTDouble / Triple Trailers
Drivers pulling double or triple trailers where those combinations are lawful. In practice, the vehicle combination normally requires a Class A CDL.
TESTINGKnowledge test
ELDTFederal ELDT not required for T alone
Who commonly needs it
- Two-trailer linehaul combinations
- Turnpike doubles where authorized
- Triple-trailer combinations where authorized
- Less-than-truckload terminal-to-terminal operations
Federal-baseline requirements
- 1Hold the CDL class required for the combination
- 2Pass the Double/Triple Trailers knowledge test
- 3Know coupling order and proper placement of the heaviest trailer
- 4Confirm that the route and state allow the planned combination
- 5Comply with equipment, length, weight and operating restrictions
What the test or training covers
Assembly, coupling and unit hookupHeaviest-trailer placementOff-tracking, sway, steering response and rolloverBraking and stability of multiple unitsTraffic effects, passing time, grades, spray and aerodynamic buffeting
Important distinctionThe T endorsement does not itself make triples legal everywhere. State law, route rules and vehicle configuration still control where the combination may operate.
06
XCDL ENDORSEMENTTank + HazMat
Drivers operating a qualifying tank vehicle that also carries hazardous materials requiring placards. X combines the Tank Vehicle and Hazardous Materials endorsements.
TESTINGTank + HazMat knowledge requirements and TSA screening
ELDTHazMat ELDT required for first-time X/H authority
Who commonly needs it
- Placarded fuel tankers
- Chemical cargo tanks
- HazMat tank containers meeting the N thresholds
- Other qualifying tanks carrying placarded material
Federal-baseline requirements
- 1Meet every N endorsement requirement
- 2Meet every H endorsement requirement
- 3Complete first-time HazMat ELDT theory with a listed provider
- 4Pass both applicable knowledge-test content areas
- 5Complete TSA's Security Threat Assessment
- 6Hold the CDL class required by the vehicle
What the test or training covers
All tanker surge, braking and rollover topicsAll HazMat shipping-paper and placarding topicsCargo-tank loading, segregation and routingEmergency response for hazardous cargo tanksSecurity awareness and safe attendance procedures
Important distinctionX is a combined credential, not a shortcut. The driver must maintain the security clearance and satisfy both the N and H operating requirements.
TRAINING CHECK
Which endorsements require ELDT?
Federal ELDT applies only the first time an applicant seeks H, P or S. Training must come from a provider listed on the FMCSA Training Provider Registry.
EndorsementTheoryBehind the wheelBefore which test?
H — HazMat
Required
Not required
Before H knowledge test
P — Passenger
Required
Range + public road
Before P skills test
S — School Bus
Required
Range + public road
Before S skills test
N — Tank
Not federally required
Not federally required
State knowledge test
T — Doubles/Triples
Not federally required
Not federally required
State knowledge test
X — Tank + HazMat
H training applies
Not for H/N alone
Before H knowledge test
ELDT is a training prerequisite; it does not replace state knowledge tests, skills tests, TSA screening or other state requirements.
STEP-BY-STEP
How to add an endorsement
Match the operation
Identify the vehicle class, passenger use, tank capacity, trailer configuration and whether the load requires placards.
Check your state
Use the current state CDL manual for forms, fees, appointment rules and test sequence.
Complete ELDT
For a first H, P or S, train with a provider listed on the FMCSA Training Provider Registry.
Complete special screening
For H or X, finish TSA's Security Threat Assessment and required identity/fingerprint steps.
Pass required tests
Take the endorsement knowledge test. P and S also require a representative-vehicle skills test.
Verify the credential
Before operating, confirm the endorsement and any restrictions are correctly printed on the CDL.
CLP RULE
49 CFR 383.93 Only P, S and N may appear on a commercial learner’s permit.
Federal rules do not permit H, T or X on a CLP. P and S CLPs also carry operating limitations during supervised practice; always follow the restrictions printed by your state.
OFFICIAL SOURCES
Federal rules used for this guide
Reviewed September 9, 2026. State procedures, fees, test counts and renewal timing may differ, so verify the current state CDL manual before applying.
NEXT STEP
Practice tests Prepare for endorsement testing.
Review the requirements, then take the matching full-length practice test.