Taxes in Longmont
Longmont's tax picture layers a genuinely fragmented, five-piece combined sales tax rate on top of a Boulder-County-typical property tax rate and Colorado's own flat, TABOR-variable state income tax -- real complexity worth walking through piece by piece rather than a single citywide number.
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Learn moreA five-layer combined sales tax rate, varying by ZIP
Longmont's sales tax stacks five separate pieces: City of Longmont (3.53%), Colorado state (2.90%), RTD (1.00%), the Scientific & Cultural Facilities District (0.10%), and Boulder County (1.335%, effective January 1, 2026) -- a combined rate cited between 8.865% and 9.335% depending on the exact ZIP code, consistent with Colorado's genuinely fragmented home-rule local sales tax system described at the state level.
Property tax: a real, ZIP-varying rate above the state median but below the national one
The City of Longmont's own municipal levy is 13.42 mills. Ownwell cites a citywide median effective property tax rate of 0.52% (a separate source rounds to 0.54%), with ZIP-level variation from 0.57% (80501) to 0.59% (80503) depending on school-district and special-assessment-district layers. This runs modestly above Colorado's ~0.49%-0.50% state median but well below the national median -- consistent with this dataset's treatment of Boulder and Fort Collins, LOW_PROPERTY_TAX is not applied here.
Colorado's flat, TABOR-variable state income tax applies as elsewhere in the state
Colorado's flat state income tax rate is 4.40% for 2026, though a TABOR-driven refund mechanism can temporarily reduce it in years the state certifies a qualifying revenue surplus (it reduced the rate to 4.25% for tax year 2024 specifically) -- see the Colorado state record for the full mechanism. This applies in Longmont exactly as it would anywhere else in the state.
Key takeaways
- Longmont's combined sales tax rate runs 8.865%-9.335% depending on ZIP code, stacking city (3.53%), state (2.90%), RTD (1.00%), Cultural District (0.10%), and Boulder County (1.335%) rates.
- The City of Longmont's own municipal property tax levy is 13.42 mills; citywide effective property tax rate is cited at roughly 0.52%-0.54%, with ZIP-level variation from 0.57%-0.59%.
- Colorado's flat state income tax is 4.40% for 2026, subject to a TABOR mechanism that can temporarily reduce it in state revenue-surplus years (as it did to 4.25% for 2024).
- Longmont's property tax rate runs modestly above Colorado's own state median but well below the national median -- not a below-state-average outlier.
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