A CDL driver who tests positive on a DOT test or refuses to take a DOT test, must successfully complete the return-to-duty (RTD) process with a DOT qualified substance abuse professional (SAP).  The requirements for the RTD are found in [49 CFR Part 40, Subpart O].
For more information visit clearinghouse.fmcsa.dot.gov or call the FMCSA Drug and Alcohol Clearinghouse, 1-844-955-0207. For a more detailed FMCSA overview of the DACH process for employers visit DACH Employer Instructions.