https://mtrevenue.gov/2022/02/07/senate-bill-376-revised-montanas-income-apportionment-formula/

Pursuant to SB 376 (2021), for tax years beginning after June 30, 2021, all multistate businesses operating in Montana will use a new calculation that double-weights the receipts factor.

Previously, taxpayers in Montana used an equally-weighted three-factor apportionment formula, comprised of a business’s property, payroll, and receipts in an equal 1:1:1 ratio with three factors.

The new calculation includes a 1:1:2 (property : payroll : receipts x 2) ratio and increases the number of factors in the apportionment calculation to four.