(1) A taxpayer must provide information the department requests to ascertain the correctness of a return within 30 days after the date of the request or obtain the department's consent to provide the information at a later date. If the taxpayer does not provide this information within 30 days, or as agreed upon, the department will adjust or disallow any amount or item that remains unverified. If the request is in writing, the 30 days are computed from the date of the written request.

(2) If a taxpayer does not file a delinquent return within 30 days after the date of a written request to file the return or obtain the department's consent to file the return at a later date, the department will estimate the taxpayer's taxable income.

(3) Failure to supply the information requested or to file a requested return will result in the assessment of tax and the assessment of interest and penalty as provided in 15-1-216 , MCA.