If any person neglects or refuses to file any report required by this chapter, the Commissioner shall make an estimate of the tax due, based upon information available to the Commissioner, for the period for which that person failed to make the report, and shall assess the tax due from the licensee, adding to the amount thus determined a penalty of 50 percent. In estimating the tax due from a licensed user, fuel consumption shall be computed at the rate of 10 miles per gallon for vehicles registered up to 10,000 pounds and four miles per gallon for those vehicles registered over 10,000 pounds. The assessment shall bear interest at the rate of one and one-half percent per month from the date the tax payment was due until paid. The Commissioner shall give the licensee notice by mail of the assessment and payment shall be due within 15 days of the date of the mailing of the notice. (Added 1981, No. 172 (Adj. Sess.), § 1; amended 1985, No. 58, § 4, eff. May 16, 1985; 1987, No. 111, § 4; 1987, No. 241 (Adj. Sess.), § 8.)