Taxes in Boulder
Colorado charges a real, flat 4.4% state personal income tax as of 2026 -- a genuinely different structure from the no-income-tax states covered elsewhere in this project, and a different rate than the flat 2.5% used by Arizona markets covered earlier -- alongside a combined sales tax rate in Boulder specifically cited at 9.195% (2.9% state, 1.335% Boulder County, 3.86% City of Boulder, and a 1.1% special district component), a figure independently sourced for Boulder and not assumed identical to Denver's or Colorado Springs's local rates.
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Learn moreColorado's Flat 4.4% State Income Tax, With a TABOR Wrinkle
Colorado applies a flat 4.4% state income tax rate to wages and most other income, per Tax Foundation and multiple 2026 tax-guide sources -- reduced from 4.55% by Proposition 121, passed by voters in November 2022. Colorado's constitutional Taxpayer's Bill of Rights (TABOR) requires the state to refund excess revenue to taxpayers in high-growth years, which has in recent years temporarily reduced the effective rate below the 4.4% statutory figure -- a real, distinctive Colorado mechanism not present in most other states covered in this project. This is a structural difference worth stating plainly: Colorado is neither a no-income-tax state (like Texas, Tennessee, or Florida) nor a flat-2.5%-rate state (like Arizona) -- it has its own real, if moderate, flat-rate income tax.
Boulder's Combined Sales Tax Rate: Independently Verified for Boulder Specifically
The minimum combined 2026 sales tax rate for the City of Boulder is cited at 9.195% by Avalara, composed of Colorado's 2.9% state rate, Boulder County's 1.335% rate (increased from 1.185% effective January 1, 2026), the City of Boulder's own 3.86% local rate, and a 1.1% special district component. Because Colorado is a home-rule state where cities set their own local sales tax rates, this figure is specific to Boulder and should not be assumed to match Denver's or Colorado Springs's combined rates, which differ and are sourced separately in this dataset's coverage of those markets. The exact rate can also vary slightly within Boulder depending on whether a specific address falls in an additional special taxing district.
Colorado Has No State Estate or Inheritance Tax
Colorado does not levy a state estate tax or inheritance tax -- a real, if secondary, tax advantage relative to the small number of states that do impose one. This detail was not the focus of deep sourcing this pass and should be confirmed against current Colorado Department of Revenue guidance for anyone making estate-planning decisions on this basis.
Property Taxes (Summary -- See Full Topic Page)
Property tax is a comparatively simpler, lower-rate category for a Boulder homeowner than the income and sales tax picture above -- Boulder County's effective rate is cited around 0.54%-0.57%, well below the national median even though it runs modestly above Colorado's own state median. See the property-taxes topic page for the full breakdown, including how ZIP-level and county-level rates vary within Boulder County.
Key takeaways
- Colorado's flat 4.4% state income tax (reduced from 4.55% by 2022's Proposition 121) is a real, structural difference from no-income-tax states like Texas/Tennessee/Florida and from Arizona's flat 2.5% rate covered elsewhere in this project.
- Colorado's TABOR provision can temporarily reduce the effective income tax rate below 4.4% in high-revenue years via automatic taxpayer refunds -- a distinctive Colorado-specific mechanism.
- Boulder's combined sales tax rate is independently cited at 9.195% for 2026 (2.9% state + 1.335% county + 3.86% city + 1.1% special district) -- not assumed identical to Denver's or Colorado Springs's rates, which genuinely differ under Colorado's home-rule system.
- Colorado levies no state estate or inheritance tax -- confirm current Department of Revenue guidance before relying on this for estate planning.
- Property tax is the comparatively lower-rate category for Boulder homeowners (0.54%-0.57% effective rate) -- see the property-taxes topic page for the full breakdown.
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