When transporting hazardous materials in a tank, what additional endorsement is required?

A driver hauling hazardous materials in a tank needs both the N (tank vehicle) and H (hazmat) endorsements. The X endorsement is a combined credential that demonstrates both, and many drivers obtain it in one process to save time. The hazmat endorsement requires a TSA security threat assessment in addition to the written test; the tank endorsement requires only the written test. Many common loads — gasoline, jet fuel, propane, anhydrous ammonia, acids — require both. The combination of tank handling and hazmat compliance is one of the most consequential CDL roles; both endorsement tests reflect that responsibility.