Boulder County sales tax rate increases in 2026
This is a county-level change, but it will raise the combined sales tax rate in multiple cities and special districts within Boulder County. Sellers must ensure county tax calculations are updated for all affected locations starting on the effective date.
Written by Alex Lamachenka
Head of DemandGen
Published
What changed
- Previous rule: Boulder County sales tax applied at a lower county rate.
- New rule: Boulder County sales tax increases to 1.335 percent.
- Effective date: January 1, 2026.
Why this matters for cities inside Boulder County
Although the rate change is enacted at the county level, it affects the total tax charged in every jurisdiction where Boulder County tax applies. For example, sellers making taxable sales in the City of Longmont will see a higher combined rate, even though Longmont’s city sales tax rate itself is unchanged.
This type of county-driven change can impact:
- Cities
- Home-rule municipalities
- Special districts
- Destination-based ecommerce transactions
Example: updated combined rate in Longmont
For transactions sourced within Longmont and Boulder County, the new combined rate will be:
- State of Colorado: 2.900%
- RTD/CD: 1.100%
- Boulder County: 1.335%
- City of Longmont: 3.530%
- Combined total sales tax rate: 8.865%
Who this affects
- Sellers with physical locations anywhere in Boulder County
- Remote sellers shipping taxable goods into Boulder County
- Ecommerce businesses collecting Colorado destination-based sales tax
- CPAs and accountants managing Colorado sales tax compliance
Next steps for sellers
- Update sales tax calculation to apply the new Boulder County rate for all affected locations starting January 1, 2026.
- Review combined rates in cities and special districts within Boulder County to confirm downstream impacts.
- After calculation is correct, ensure January 2026 transactions are reported accurately on February 2026 sales tax returns.
Other US Sales Tax Updates
Georgia county sales tax rate changes effective January 1, 2026
Georgia has announced multiple county-level sales tax rate changes effective January 1, 2026. Sellers should review affected counties and confirm rate updates before the new year.
Colorado eliminates state sales tax service fee starting January 1, 2026
Colorado has eliminated the state-level sales tax service fee. Sellers must now remit 100% of Colorado state sales tax collected, even if sales volume and tax rates remain unchanged.
Sitka, Alaska just declared Nov 28–29, 2025, as sales tax-free days
Sitka, Alaska has announced sales tax-free days for Black Friday weekend. It won’t affect most ecommerce sellers, but it’s a reminder that local quirks can pop up in your compliance map.