Montana estimated tax (quarterly) calculator

Plan quarterly payments based on Montana tax rules.

How this calculator works

Step 1 estimates your Montana tax based on the taxable income you provide and the Montana 4.7%/5.9% brackets. The tool adjusts for Montana-only income using your allocation %.

Step 2 uses your withholding and prior-year tax (if provided) to estimate a quarterly plan that aligns with Montana’s 90% current-year or 100% prior-year safe-harbor rules.

Step 3 divides the remaining tax into four equal payments and lists the standard due dates used by Montana.

Frequently asked questions

When are Montana estimated payments due?

Montana uses the standard quarterly dates: April 15, June 15, September 15, and January 15 of the following year.

What if withholding changes later?

Recalculate with updated withholding to keep your quarterly plan accurate.

Is the safe harbor the same as federal?

Montana generally follows a 90% current-year or 100% prior-year safe harbor. Special rules apply if at least two-thirds of your income is from farming or ranching.

Estimates use Montana’s published brackets (4.7%/5.9%) and are not a substitute for official payment calculations.