Boulder County Property Taxes: Mill Levies, Lookup and Due Dates

Boulder County property tax: the 2025 mill levy, how to look it up and when it is due

Boulder County property tax for a home in the City of Boulder runs 89.200 mills for tax year 2025 (paid in 2026) in the base tax area, and the Boulder property tax rate changes with the address: across the county's 365 tax areas the total runs from 54.018 to 201.089 mills. That is why two Boulder County homes at the same price can have very different bills. This guide shows the county's 2025 levies, a worked tax bill, how to do a Boulder County property tax lookup, when payments are due and how to appeal a value. Call or text 303-955-4220. A live person answers. The Kenna Group at Keller Williams DTC.

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A Boulder County tax bill, from value to dollars

The county's own formula has four steps. The Assessor sets an actual value. For tax year 2025 the state's residential assessment rates are 7.05% for school districts and 6.25% for every other local government, which gives two assessed values. Each taxing authority's levy is then applied to its assessed value. A mill is $1 of tax for every $1,000 of assessed value. The $55,000 residential value reduction that lowered 2024 bills ended for 2025, according to the county.

Example: base City of Boulder tax area, 2025 levies

Illustration only, using the county's 2025 levies for tax area 0010 (Boulder Valley schools, Boulder County, City of Boulder, Boulder Public Library, Northern Colorado Water and Urban Drainage) and the 2025 assessment rates. Your address may sit in a different tax area, and the senior exemption and other reductions are not shown.

Boulder County property tax by town

Each town has several tax areas, depending on its fire district, library, water and metro districts. Here is the range the county published for 2025:

Outside these eight towns, the county's other 217 tax areas run from 54.018 to 159.144 mills. Erie also extends into Weld County, which is not in this list. The same $900,000 actual value works out to about $5,361 in Lafayette (tax area 0110), $5,363 in Boulder (0010), $5,472 in Louisville (0090), $5,905 in Longmont (0680) and $6,785 in an Erie area served by St. Vrain Valley schools (1389). St. Vrain Valley's 57.717 school mills compare with Boulder Valley's 48.044, which explains much of the gap. These are illustrations, not quotes for a specific home.

What the county levied in 2025

Boulder County's Board of Commissioners adopted its 2026 budget on December 9, 2025 and levied 24.046 net mills for tax year 2025 under Resolution 2025-059. That is 24.645 gross mills less a 0.932 temporary credit plus a 0.333 abatement levy. The pieces: general operating levies 22.245 gross, plus voter-approved levies of 1.000 for developmental disabilities, 0.500 for health and human services and 0.900 for a second voter-approved human services fund. The Assessor certified net taxable assessed value of $11,631,881,772, up about 0.77% from 2024. Other 2025 levies from the county's mill levy changes list: Boulder Valley School District 48.044 (2024: 48.175), St. Vrain Valley School District 57.717 (2024: 57.168), City of Boulder 11.648 (unchanged), Boulder Public Library District 3.562 (2024: 3.500). The county says it receives about a quarter of the property tax collected, and the Treasurer distributes tax for 135 taxing entities.

Open Boulder County Property Search, the Treasurer's property tax page and the Assessor's mill levies and taxing districts page. The county explains the math on its property tax calculation page. Phone: Assessor 303-441-3530, Treasurer 303-441-3520.

Boulder County property tax due dates and late fees

Property tax is paid a year behind: the 2025 tax is due in 2026. Notices are mailed near the end of January. Payment options for 2026: two half payments due March 2 and June 15, or the full payment by April 30. There is no discount for paying early. Mailed payments count on the postmark date, and the county does not accept cash by mail. After September 1 the county accepts only certified funds. If you have a mortgage escrow account, your lender normally pays the bill; confirm it with your servicer.

Late payments carry a percentage that depends on the month. The Treasurer's published schedule:

For September through December, contact the Treasurer, 303-441-3520. See the Treasurer's due dates page for the current schedule and online payment status.

Appeals, exemptions and relief

Value appeals. The Assessor revalues every property in odd-numbered years, using sales through June 30 of the prior even-numbered year. Notices of Valuation are mailed on May 1 of the reappraisal year. In 2025 the appeal window ran from May 1 to early June (the county announced a June 9 deadline). The Assessor mails a Notice of Determination on or before August 15, and you can then take an appeal to the Board of Equalization by September 15. The next reappraisal is in 2027. You can appeal the Assessor's value but not the tax rate: levies are set by the taxing districts' budgets, not by the Assessor. See the Assessor's appeals page.

Senior and veteran exemptions. Qualifying seniors can exempt half of the first $200,000 of actual value of a primary residence, up to $100,000 of value, and the state pays the tax on the exempted value. For tax year 2026 an applicant must have been born on or before January 1, 1961 and owned and lived in the home since before January 1, 2016. Applications for tax year 2027 open after January 1, 2027. The disabled veteran exemption is for veterans with a 100% permanent service-connected disability who own and occupy the home. Details are on the county's senior exemption page and in our Colorado senior property tax exemption guide. The Treasurer also accepts property tax deferral applications from January through mid-March for taxes due that year.

2026 rule change. For tax year 2026 (paid in 2027) the school rate stays 7.05%, while the local government rate becomes 6.8% after subtracting 10% of the first $700,000 of actual value. The 2026 levies will not be known until the districts certify their budgets in December 2026.

Metro districts and other special districts in Boulder County

A metro district adds its own levy on top of the county, school and town. From the county's 2025 list: Superior Town Center Metropolitan Districts 1, 2 and 3 levy 74.650, 49.421 and 35.307 mills; Parkdale Metropolitan Districts 1, 2 and 3 levy 73.546, 69.812 and 16.105; Erie Farm Metropolitan District 55.585; Weems Neighborhood Metropolitan District 63.265; Mountain Brook Metropolitan District 54.885; Knollwood Metropolitan District in Boulder 20.570. Those are the district's own mills and add to the base stack. Our special district and metro district tax guide explains what to ask for, and the Denver property tax guide shows the same method for Denver.