Mont. Code Ann. § 15-32-610

In addition to all other deductions from Montana taxable income allowed in computing taxable income under Title 15, chapter 30, or from gross corporate income allowed in computing net income under Title 15, chapter 31, part 1, a taxpayer may deduct an additional amount equal to 10% of the taxpayer's expenditures for the purchase of recycled material that was otherwise deductible by the taxpayer as business-related expense in Montana.