Taxes in Thornton
Colorado's flat 4.4% state income tax (2026) applies to Thornton residents same as anywhere else in the state, layered with a combined sales tax that runs approximately 8.5%-8.8% for the city's Adams County portion -- with the Weld County portion's specific rate not independently confirmed this pass.
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Learn moreColorado's flat 4.4% income tax -- restated as place-level context
Colorado applies a flat 4.4% state income tax rate for 2026 to all taxable income regardless of filing status, per the Tax Foundation, AARP, and NerdWallet, independently verified this session. See colorado-tier-a-1.js for the full statewide record.
Thornton's own layered municipal sales tax, with a real small cross-source disagreement
Thornton's own municipal sales tax is 3.75%, layered on Colorado's 2.9% state rate, a 1.0% RTD rate, a 0.75% Adams County rate, and a 0.10% SCFD rate for the Adams County portion of the city -- a combined 8.5% per the city's own tax-explainer page. A separate 2026 aggregator cited a slightly higher combined figure of 8.8% for the same general period -- a real, small, disclosed disagreement. Because Thornton also extends into Weld County, which is not part of the RTD/SCFD special districts, the Weld County portion likely carries a different combined rate, though this specific figure was not independently resolved this pass.
Property tax: three close, but not identical, figures
Adams County's effective property tax rate was cited at both 0.66% and a separately cited 0.60% across two different 2026 sources, while a Thornton-specific median effective rate was cited at 0.65% -- three genuinely close but not identical figures, disclosed rather than picked from arbitrarily. Confirm an actual bill directly with the Adams County Assessor for a specific property.
No state estate or inheritance tax
Colorado does not levy a state estate tax or inheritance tax, consistent with the statewide record -- though Colorado residents with sufficiently large estates may still owe the federal estate tax. Confirm current guidance for any actual estate-planning decision.
Key takeaways
- Colorado's flat 4.4% state income tax (2026) applies to all Thornton residents regardless of filing status.
- Thornton's combined sales tax runs approximately 8.5% (city's own figure) to 8.8% (a separate 2026 citation) for its Adams County portion -- the Weld County portion's rate wasn't independently confirmed this pass.
- Adams County effective property tax rate citations ranged 0.60%-0.66%, with a Thornton-specific median cited at 0.65% -- three close but not identical figures; confirm an actual bill directly with the Adams County Assessor.
- Colorado levies no state estate or inheritance tax, though the federal estate tax can still apply to sufficiently large estates.
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