SCACs are required when doing business with all U.S. Government agencies and with many commercial shippers including, but not limited to, those in the automobile, petroleum, forest products, and chemical industries as well as suppliers to retail businesses and carriers engaged in railroad piggyback trailer and ocean container drayage. Carriers who use the Uniform Intermodal Interchange Agreement (UIIA) are required to maintain a valid SCAC. The petroleum industry uses SCACs in their integrated software programs that expedite the movement of bills of lading, pipeline tickets, product transfer orders, and inventory data. Many commercial shippers and receivers utilize SCACs in their freight bill audit and payment systems.

A fuel tax liability is created when the amount of fuel consumed is larger than the amount of fuel purchased in a particular state during any one-tax quarter. If the state charges a fuel surcharge over and above the specific fuel tax levied, it will generally be charged on the total amount of fuel consumed within that state during that same quarter regardless of the amount of fuel purchased within that same state. Anytime there is more fuel purchased than consumed in a particular state during a tax quarter a fuel tax credit is created and is used to offset any fuel tax liability during that same quarter.