Mont. Code § 15-37-106
If a person fails to file the required statement of gross yield for a reporting period on or before the date the tax becomes delinquent under 15-37-108, the department shall, immediately after the time has expired, determine as nearly as may be possible from any returns or reports filed with any state or county officer or board under any law of this state and from any other information that the department may be able to obtain the total gross value of product of the person from the business during the reporting period for which the license tax is to be paid. The department shall file a statement showing the amount of the gross value of product and shall determine and assess the amount of the license taxes due from the person. The department shall, as soon as possible, give notice to the person in the same manner as though the statement had been filed within time. The department shall collect the license tax, along with penalty and interest as provided in 15-1-216.
§ 15-37-106, MCA