2026 fiscal calendar
Know the tax date before it becomes a penalty date.
Tax bills, payment rules, and valuation-review windows are controlled by the local jurisdiction and the governing state framework. The verified record below separates published figures from dates that require confirmation with Granite County Treasurer / Superintendent of Schools / Montana Department of Revenue Property Assessment Division.
Effective rate
no single countywide effective rate was published; Montana county, municipal, school, and special-district mill levies vary by taxing jurisdiction.
Statement mailing
the official county treasurer page reviewed does not publish a specific 2026 real-property tax-bill mailing date.
Payment deadline
Tax year 2026 real-property taxes: first payment due by 5:00 p.m. November 30, 2026 or within 30 days of the postmark on the tax notice, whichever is later; second payment due by 5:00 p.m. May 31, 2027. If a due date falls on a weekend or holiday, the next business day applies.
Valuation protest
For the 2025–2026 valuation cycle, submit Montana DOR Form AB-26 within 30 days of the classification and appraisal notice, or file directly with the county Tax Appeal Board within 30 days. The 2026 fallback informal-review deadline was June 1, 2026. A written protest must also be filed with the county treasurer and disputed taxes paid under protest by the tax-payment due date.
Critical payment warning
Do not assume a grace period.
The verified county record identifies the payment timing above but does not establish a universal penalty schedule for this page. Late charges, interest, collection costs, tax-sale procedures, and lien or foreclosure timelines can depend on state law and the local collector’s process. If the deadline is close or a balance is delinquent, contact the tax collector directly and request the current payoff amount in writing.
Treat the published payment deadline as a hard operational date and retain your receipt or confirmation number.
Read the calendar in order
From assessment to collection
1. Valuation and notice
Review the assessment notice as soon as it arrives. The protest window may run from the notice date rather than from the payment due date.
2. Statement and account review
Match the tax statement to the parcel or account number and confirm exemptions, assessed value, taxing units, credits, and balance.
3. Payment confirmation
Use the official collector channel, then save the receipt, transaction reference, and date posted. A bank submission is not always the same as a county posting date.