Mont. Code Ann. § 15-35-106

The Montana state bureau of mines and geology shall test coal production subject to this chapter and may make rules governing the collection of test data. A person subject to this chapter shall submit to the bureau on or before August 1 each year a sample of mine-run, "as is" coal from each mine producing that year. Additional samples shall be submitted at the request of the bureau. The bureau shall compute the Btu per pound of each sample received and forward this information to the department prior to September 1 each year.