Answer from Former Drug and Alcohol Program Manager for the US Coast Guard, Robert Schoening ...
There are no mandatory reporting requirements for C/TPAs. The regs are that the marine employer is responsible for all reporting requirements including positive test results and MIS.
With that stated, marine employers can elect to have a C/TPA do their MIS reporting but then there are requirement on the C/TPA. Even if a C/TPA does the MIS reporting, that does not absolve the responsibility of the employer. The marine employer has a responsibility to ensure the accuracy of their data being submitted by the C/TPA.
The C/TPA has the responsibility of compiling all the data, prepare a list of all the marine employers that the data is for. The name and address should be included for each marine employer plus the vessel identification number as issued by the Coast Guard or for state registered vessels, the state registration number The state registration number begins with the State abbreviation code followed by 3 or 4 numbers then can be followed by another one or two digit alpha id.
The state ID number is for those vessels that are non-inspected and operated by licensed operator to carry no more than 6 passengers. Side note: If the Coast Guard stops an operator with 7 or more passengers, that operator might as well surrender their license on the spot.
A C/TPA can elect to report all non-negatives to the Coast Guard but an information copy should be sent to the marine employer for their records and in the event of an inspection to demonstrate compliance.