What is an MCS-150B correction?
MCS-150B is the form variant for hazardous-materials-related updates to the carrier's registration. Carriers that newly transport hazmat, change their HM-cargo classification, or change their HM operations file MCS-150B instead of the standard MCS-150. The form covers the same core fields as MCS-150 plus hazmat-specific data (HM cargo types, HM operations).
The FMCSA MCS-150 family has three variants for different carrier categories: MCS-150 (general motor carrier), MCS-150B (hazardous materials carrier), and MCS-150C (intermodal equipment provider). The B and C variants share the core fields with the base MCS-150 plus category-specific data sections. Hazmat carriers file MCS-150B for both initial registration and biennial updates as long as they continue to transport hazardous materials.
The HM-specific data on MCS-150B includes: types of hazardous materials transported (Division 1.1, 1.2, 1.3 explosives; Class 7 radioactive materials; etc.), HM operations classification (carrier, shipper, both), and any FMCSA-issued HM safety permits. These fields drive the carrier's SMS HM-Compliance BASIC score and feed into FMCSA hazmat enforcement priorities.
A carrier that newly enters hazmat transportation files MCS-150B to update its registration from non-hazmat to hazmat status. Conversely, a carrier that exits hazmat transportation files MCS-150 (without B) on its next biennial update to remove the HM classification. Mid-cycle changes can be filed at any time — the §390.19 30-day window for any operations change applies.
For carriers with mixed hazmat and non-hazmat operations, MCS-150B captures the full picture in one form. The fleet vehicle count includes both hazmat-rated and non-hazmat trucks; the mileage fields cover all interstate operations regardless of cargo type. Only the HM-specific data sections distinguish hazmat from non-hazmat operations.