How to File Sales Tax in Colorado: Form DR 0100 and Deadlines

To file sales tax in Colorado, you gather your period’s sales figures, complete Form DR 0100 (the Colorado Retail Sales Tax Return), and submit it with payment through Revenue Online by the 20th of the month after your filing period ends.¹ You have to file for every assigned period, even one where you made no taxable sales. Skipping a “zero” period is one of the fastest ways to draw penalties and put your license at risk.²

When Your Return Is Due

The Department of Revenue assigns your filing frequency based on how much sales tax you collect each month:

Monthly filing if you collect $600 or more in tax per month. Returns are due the 20th of the following month.
Quarterly filing if you collect less than $600 per month. Returns are due the 20th of the month after the quarter ends.
Annual filing if you collect $15 or less per month. The return is due January 20 of the following year.

Wholesale businesses with total annual sales tax liability of $180 or less can also file annually.³ When the 20th falls on a weekend or legal holiday, the deadline shifts to the next business day.⁴

What to Have Ready Before You File

Pull together your total gross sales for the period, a breakdown of any nontaxable revenue, and your Colorado Account Number (which is different from your federal EIN or Social Security number).⁵ Common exemptions include sales to government entities, wholesale transactions where the buyer is reselling the goods, and shipments delivered outside Colorado.⁶

Keep the paperwork that backs up each exemption. When a customer claims a resale or wholesale exemption, they should give you a completed Form DR 0563 or the equivalent Multistate Tax Commission certificate, and you must retain a copy.⁶ Without it, the Department can reclassify the sale as taxable during an audit, and you’ll owe the tax plus interest. Records should be kept for at least three years, since the Department can request invoices and purchase documentation going back that far.⁷

If you operate multiple locations, separate your sales data by site. Each physical location has its own license and files its own return.

Filling Out Form DR 0100

Form DR 0100 walks you through the math line by line.⁸ Enter gross sales, subtract exempt and nontaxable amounts, and arrive at net taxable sales. Apply the state sales tax rate of 2.9% to that figure.⁹

Below the state calculation, enter the applicable local tax rates for the city, county, or special district where each sale occurred. Rates vary widely across Colorado; look them up in the Department’s DR 1002 publication or through Revenue Online.⁸ If you have more than one business location, file a separate return for each.¹

The Service Fee Change in 2026

Colorado used to let retailers keep a small percentage of the state sales tax they collected as a service fee, or vendor fee, to compensate for the cost of processing returns. That state-level service fee is gone. Beginning January 1, 2026, retailers can no longer retain any portion of the state sales tax.¹⁰

Local jurisdiction service fees still exist. Many cities, counties, and special districts continue to allow one, with rates that vary by jurisdiction; some, for example, offer a 3.33% service fee on local taxes collected.¹¹ Check DR 1002 for the rate that applies to your location. You only qualify for the local service fee if you file and pay on time. Late filing disqualifies you entirely.¹⁰

When filing an amended return for an earlier period, use the service fee rate that was in effect during the original filing period, not the current rate.³

Submitting and Paying Through Revenue Online

Once your return is ready, submit it through Revenue Online. Log in with your credentials, go to your business tax account, and select the filing period. Enter the figures from your prepared DR 0100, review, and submit. The system generates a confirmation number that serves as your proof of filing.¹

Payment must accompany the return. You can pay by electronic funds transfer, credit card, or e-check. Save or print both the filing confirmation and the payment receipt. Those records protect you if the Department later asks whether you filed or paid on time.

Home-Rule Cities Aren’t Covered on Your DR 0100

Colorado’s counties and cities whose sales tax is collected by the Department are “state-collected” jurisdictions, and their local taxes appear on the same DR 0100 alongside your state tax.¹²

Home-rule cities are different. These municipalities have adopted their own charters and administer their own sales tax independently. If you make sales into a home-rule city, you generally need to register with that city, file a separate return on their schedule, and follow their rules about what is and isn’t taxable. Home-rule cities can tax different goods and services than the state does, and their exemptions may not mirror the state’s. Nearly all Colorado counties are state-collected, with Denver and Broomfield the notable exceptions.¹²

If You Sell From Out of State or Through a Marketplace

An out-of-state business must collect and remit Colorado sales tax once its sales into the state exceed $100,000 in the current calendar year. If you crossed that threshold in the previous year, you’re subject to collection for the entire following year. Once you exceed the threshold, you have until the first day of the first month that begins at least 90 days later to obtain a license and begin collecting. Businesses that stay below $100,000 in both the current and previous years are exempt from collecting, but they still owe transactional notices to Colorado purchasers, an annual purchase summary to each buyer by January 31, and an annual customer information report to the Department by March 1.¹³

If you sell through a platform such as Amazon or Etsy, the marketplace facilitator is generally responsible for collecting and remitting Colorado sales tax on sales made through its platform. That duty cannot be pushed back onto you.¹⁴ The facilitator must collect state and state-administered local taxes on every taxable sale through its platform, even for individual sellers who wouldn’t otherwise meet the threshold.¹⁵ If you also sell directly through your own website or a physical store, you still need your own license and file separately for those non-marketplace sales.

What Happens If You File Late

Late filing or late payment triggers penalty and interest right away. The sales tax penalty is the greater of $15 or a percentage of the unpaid tax equal to 10% plus 0.5% for each month the tax remains unpaid, capped at 18% total.¹⁶ Interest also accrues on the unpaid balance. For 2026, the discounted rate is 8% annually if you pay before receiving a notice of deficiency, or within 30 days of one. Wait longer and the regular 11% rate applies.¹⁷

Late payment also disqualifies you from the local service fee for that period. And if the Department finds fraud or willful failure to file, the penalties are far steeper.¹⁶

Fixing a Mistake After You File

If you catch an error after submitting, file an amended DR 0100 for the same period. Check the “Amended Return” box and enter corrected figures for every tax column, not just the lines that changed. The amended return replaces the original entirely.³

If the correction results in an overpayment, you can take a credit on your next regular return. If you underpaid, file a separate amended return for that period and pay the difference. A business that has closed and later finds a prior overpayment applies for a refund using the Seller’s Claim for Refund.³

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Department of Revenue – Taxation. File Sales Tax on Revenue Online
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Department of Revenue – Taxation. Zero File Sales Tax Return
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Department of Revenue – Taxation. Sales Tax Filing Information
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Department of Revenue – Taxation. Colorado Taxes and Fees Due Date Guide
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Department of Revenue – Taxation. How to Look Up a Colorado Account Number (CAN)
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Department of Revenue – Taxation. Sales Tax Guide
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Colorado Department of Revenue. Sales Tax Points of Compliance
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Colorado Department of Revenue. DR 0100 Colorado Retail Sales Tax Return
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Justia. Colorado Code 39-26-105 – Vendor Liable for Tax
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Department of Revenue – Taxation. Service Fee
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Department of Revenue – Taxation. Sales Tax Rate Changes
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Department of Revenue – Taxation. Local Government Sales Tax
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Department of Revenue – Taxation. Out-of-State Businesses
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Department of Revenue – Taxation. Marketplace Facilitators
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Colorado Department of Revenue. Sales and Use Tax Topics: Marketplaces
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Department of Revenue – Taxation. Tax Topics: Penalties and Interest
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Colorado Department of Revenue. Tax Topics: Penalties and Interest