X isn't a separate credential with its own test. It's what your CDL shows once you hold HazMat (H) and Tanker (N) at the same time. If you'll haul hazardous liquids or gases in bulk tanks, gasoline, diesel, industrial chemicals, this is the combination you need.
There's no separate X question bank to study, because there's no separate X test. This pulls directly from the real HazMat and Tanker banks, the same two knowledge tests X actually requires.
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What X Actually Is
X is a combined code, not an independent endorsement. When a driver holds both HazMat (H) and Tanker (N) simultaneously, many states display that pairing as a single X on the license rather than printing both letters separately. Order doesn't matter, some drivers get HazMat first and add Tanker later, others do the reverse. The moment you hold both, your CDL reflects X.
Job postings that say "X endorsement required" and "HN preferred" mean the same thing. If you're targeting fuel, petroleum, or chemical freight, X is the standard, expected credential.
What Each Half Actually Requires
H — HazMat
Knowledge test
TSA Security Threat Assessment ($85.25, or $41 with TWIC)
X adds nothing beyond what H and N already require individually. No combined test, no separate skills evaluation, no additional background check. You simply need to satisfy both sets of requirements above. The TSA process is the genuine bottleneck, since it's the same 30–60 day check the H side requires on its own.
Frequently Asked Questions
What is the X endorsement on a CDL?
X is not a separate, standalone endorsement. It's the code that appears on your CDL when you hold both HazMat (H) and Tanker (N) at the same time. Many states consolidate the two letters into a single X rather than printing both separately.
Do I need to take a separate X test?
No. There is no standalone X exam. You pass the HazMat knowledge test and the Tanker knowledge test, and complete the TSA background check the HazMat portion requires. Once you hold both H and N, your state applies the X code.
Does the X endorsement require a skills test?
No. Neither HazMat nor Tanker individually requires a skills test under current federal rules, and X doesn't add one.
Can I get HazMat and Tanker at different times and still end up with X?
Yes. As soon as you hold both H and N simultaneously, your CDL reflects the X combination, regardless of which order you obtained them in.
Sources: 49 CFR 383.93; TSA HazMat Endorsement Program. Last verified August 2026.
Study the Individual Endorsements
X is built from these two, dig into whichever you need first.