Among CDL endorsements, Hazmat (H) and Tank (N) are the two that most reliably increase a driver's earning potential. They're frequently added together as the combined "X" endorsement (HazMat + Tank), but they don't have to be — and the order in which you add them matters more than most new drivers realize.
Hazmat (H) — what it adds
The Hazmat endorsement authorizes you to transport quantities of hazardous materials that require federal placarding. Adding it requires passing a written knowledge exam covering placarding, segregation, loading rules, emergency response, and FMCSA hours-of-service modifications for hazmat loads. Hazmat additionally requires a TSA Security Threat Assessment — fingerprinting and a federal background check that costs $90 to $130 and can take 30 to 60 days to clear. Hazmat alone typically adds 5% to 10% to a Class A driver's pay.
Tank (N) — what it adds
The Tank endorsement authorizes you to operate any tank vehicle — baffled, unbaffled, or smooth-bore — carrying liquid or gaseous loads. The knowledge exam focuses on load surge, baffle design, slow filling and unloading procedures, and the special handling required for partial loads. Tank has no TSA requirement and no skills test of its own (you take your skills test in whatever vehicle the state approves). Tank alone typically adds 3% to 6% to driver pay, but it qualifies you for tanker dedicated lanes that often pay 15% to 25% more than dry-van freight.
The "X" endorsement combo
When you add Hazmat and Tank together, your license shows the "X" endorsement — and you become qualified for fuel hauling, food-grade tanker, chemical bulk, and many other premium specialty lanes. X-endorsed drivers consistently earn $8,000 to $20,000 more annually than base Class A drivers. The trade-off is more demanding pre-trips, longer loading and unloading times, and stricter HOS rules around hazmat placarded loads.
Which order should you add them?
If your goal is fuel or chemical tanker work, add both at once: study together, take both knowledge exams in a single visit, and start the TSA process the day you pass Hazmat. If your goal is dry-bulk tanker (cement, sand, dry food) and you don't need Hazmat, just take Tank alone — there's no need to pay for the TSA background check and re-up cycle. Drill our Hazmat study guide and Tank vehicle study guide before sitting for either exam.