Which document do you have to carry with you for a bus in cross-border traffic within the EU states?

When operating a bus in cross-border traffic within EU countries, you must carry a certified copy of your valid commercial license that authorizes you to transport passengers across borders with coaches and buses. This document proves that you are legally permitted to provide such transport services. Other documents like timetables or location descriptions are not legally required to be carried during operation. Carrying the certified license copy ensures you can verify your authorization to authorities during inspections.