Boulder County, CO tax sales
How tax lien certificate and tax deed sales work in Boulder County, seat of Boulder: sale calendar, auction platform, over-the-counter lists, and the offices that run each sale.
Verified Jul 30, 2026 against official county and state sources.
New here? Read how Colorado tax sales work, the difference between a lien and a deed, and redemption periods.
How Boulder County sells delinquent taxes
Tax certificate sale (lien)
- Run by
- Boulder County Treasurer's Office
- Frequency
- annual
- Typical timing
- November. The Treasurer's tax lien sale page states "Our tax lien sale was held Nov. 14, 2025" and its prior-year table lists sale dates of 11/5/2021, 11/16/2022, 11/17/2023, 11/8/2024 and 11/14/2025. On sale day the FAQ states "The sale will begin as soon after 8:30 a.m. as all bidders are registered" and "The auction will last until all properties are sold or until 5 p.m.", with staff deciding whether to continue or adjourn to the next business day.
- Next expected
- by the second Monday in December, 2026 (window; exact date posts closer to the sale)
Registration and deposit
Register in person on the day of the sale. The FAQ states "Registration opens at 7:30 a.m. on the day of the sale" and that "The exact spelling of the name you register with will become the name used on the tax lien certificate." Bidders provide a name, an address for checks and correspondence, a Social Security or Tax ID number, and a completed, signed IRS W-9 form. Registered bidders receive an 8 hour parking pass and park free in four downtown Boulder city lots (11th and Walnut, 14th and Walnut, 11th and Spruce, 15th and Pearl).
Boulder County runs its annual tax lien sale as a live, in-person auction, not an online auction. The FAQ gives the sale location as the Boulder County Courthouse, 1325 Pearl Street, Third Floor, Boulder, CO 80302, confirms an auctioneer conducts the sale, and states observers are allowed but seating is limited. No online bidding platform is named on any county page, so verify the format with the Treasurer's Office before planning to bid remotely. Bidding is premium bid: "The auction is open bidding" with no rotation through bidders, and "The bid amount is the premium amount", meaning the amount over and above the taxes, interest and fees on the day-of-sale list. Premium earns no interest and is not refunded; it goes to the County General Fund. The county warns this is a buyer-beware process and gives the example that a 6% premium against a 10% redemption rate loses money if the lien redeems before eight months pass. Recent premiums averaged 5.6% to 7.6% over the last five sales. The interest rate is set by the State of Colorado in September at 9 percentage points above the Kansas City Federal Reserve discount rate, rounded up to the nearest whole percent; the county lists 14% per annum for liens sold in 2025. Interest accrues monthly on the first day of the month and is paid only on redemption. The auction list is published in the county newspaper of record 4 weeks before the sale for 3 consecutive weeks (Longmont Daily Times-Call, plus the Boulder Daily Camera, Nederland Mountain Ear, Lafayette News, Louisville Times, Lyons Recorder and Colorado Daily in the final week). A current property list is posted on the Treasurer's tax lien sale page near the time of the sale and updated weekly, and printed copies are available at 1325 Pearl Street; the posted spreadsheet is taken down after each sale, so check the sale page in the fall. Boulder County does not offer tax lien certificates over the counter. Subsequent-year taxes may be endorsed onto an existing certificate for a $5 fee, at the original lien's rate, with notices mailed each August. Certificates are held by the Treasurer for safekeeping and copies are mailed within a week of the sale; certificates may be transferred if notarized, recorded with the Boulder County Clerk and Recorder, and accompanied by a new W-9. After three years of unpaid taxes from the original sale, a lienholder may apply for an auction of a Certificate of Option for Treasurer's Deed; the county says less than one half of one percent of its tax liens reach deed. Separately, the county announced a mobile home tax lien sale for Dec. 5, but states that under C.R.S. 39-10-111.5 delinquent mobile home taxes are struck off to the county rather than offered for sale at auction. Third-party aggregator sites list Boulder County sale data; treat only the Treasurer's own pages as authoritative. In person at the Boulder County Courthouse (live auction with an auctioneer)
Tax deed sale
- Run by
- County Treasurer
- Frequency
- on application
- Typical timing
- There is no fixed calendar. A public auction is scheduled only when a certificate holder applies for one, at least three years after the tax lien sale, and the treasurer must hold it between 110 and 125 calendar days after the known interested party notice is first published or mailed.
Registration and deposit
What sells is a certificate of option for treasurer's deed, not the parcel outright. The treasurer may only accept bids above the combined amount owed to the lawful holder plus the treasurer's fees and costs. County officials, county employees acting in their individual capacity, and their immediate family members may not bid. Payment is by cash, cashier's check, bank check, or electronic funds transfer subject to the treasurer's bidding rules. Any overbid goes to junior lienors who filed a notice of intent to redeem and then to the property owner. Confirm the notice, the bidding rules, and the auction venue with the county treasurer.
This Article 11.5 process replaced direct deed issuance on July 1, 2024. Colorado does not hold a routine calendar tax deed sale, so treat this as an occasional, application-driven auction rather than a recurring event.
Over-the-counter (leftover) purchases
Liens that draw no bid are struck off to the county and the treasurer issues the county a certificate of purchase. The county may then assign, sell, or transfer those certificates in the manner, at the times, and on the terms set by resolution of the board of county commissioners, which is how county-held liens are sold between annual auctions. A certificate on property owing more than ten thousand dollars in taxes needs the property tax administrator's approval after published notice. Whether a county maintains a published county-held list, and on what terms, varies. Contact the county treasurer.
New to this path? Read how over-the-counter certificates work.
County offices
Tax Collector (runs the certificate sale)
Boulder County Treasurer's Office
P.O. Box 471, Boulder, CO 80306 (public counter: 1325 Pearl St., 1st Floor, Boulder, CO 80302)
Official websiteNotes for Boulder County
- Boulder County holds a live, in-person tax lien auction at the Boulder County Courthouse, 1325 Pearl Street, Third Floor. No online bidding platform is named on the county's pages.
- Registration opens at 7:30 a.m. on sale day and requires a Social Security or Tax ID number and a signed IRS W-9; bidding starts as soon after 8:30 a.m. as everyone is registered.
- Bidding is premium bid over the taxes, interest and fees. Premium earns no interest and is never refunded, so a high premium can wipe out the interest yield if the lien redeems early.
- The 2025 rate was 14% per annum. Colorado sets the rate each September at 9 points above the Kansas City Federal Reserve discount rate, rounded up.
- The county does not sell tax lien certificates over the counter.
- Delinquent mobile home taxes are struck off to the county under C.R.S. 39-10-111.5 instead of being auctioned.
- The advertising list is posted on the Treasurer's tax lien sale page in the fall and removed after the sale, so the direct spreadsheet link changes each year.
Colorado statewide rules
- Redemption
- Redemption may be made at any time before a treasurer's deed is executed, so the practical window runs well past the three-year mark and through the Article 11.5 auction process. The treasurer must hold that public auction between 110 and 125 calendar days after the known interested party notice is first published or mailed, which gives owners and junior lienors a further defined period to pay. A separate rule lets an owner who was under a legal disability when the deed was executed redeem within nine years of the deed being recorded, at 15 percent per year plus the present value of any improvements.
- Deed deposit
- The treasurer may require the applying lawful holder to post a deposit covering the recording fee plus the actual and reasonable cost of administering the auction, and all Article 11.5 fees and costs are chargeable as additional amounts owing under the tax lien. For bidders, the treasurer accepts cash, cashier's check, bank check, or electronic funds transfer subject to the treasurer's bidding rules. The statute sets no fixed bidder deposit percentage, so the deposit terms come from county bidding rules.
- Surplus proceeds
- Any overbid goes first to junior lienors in order of recording priority, measured as of the recording date of the application for public auction, who filed a notice of intent to redeem and whose liens are unredeemed, up to each lien's unpaid amount plus fees and costs. Whatever remains is paid to the property owner. The treasurer must post a public notice about these funds and mail the owner a notice within thirty calendar days of the auction. Unclaimed remaining overbids sit in escrow for six months without interest, then transfer to the state administrator under the Revised Uniform Unclaimed Property Act. An agreement to pay someone to recover an owner's overbid is unenforceable, and inducing one is a class 2 misdemeanor.
A tax deed does not convey marketable title. Most buyers file a quiet title action before they can resell or insure the property. See the due diligence guide.
Frequently asked questions
Does Boulder County, Colorado sell tax liens or tax deeds?
- Boulder County follows Colorado's tax lien state system.
When is the Boulder County tax certificate sale?
- November. The Treasurer's tax lien sale page states "Our tax lien sale was held Nov. 14, 2025" and its prior-year table lists sale dates of 11/5/2021, 11/16/2022, 11/17/2023, 11/8/2024 and 11/14/2025. On sale day the FAQ states "The sale will begin as soon after 8:30 a.m. as all bidders are registered" and "The auction will last until all properties are sold or until 5 p.m.", with staff deciding whether to continue or adjourn to the next business day.. Registration and bidding happen on the county's online platform. Always confirm the exact date with the Tax Collector before the sale.
How often does Boulder County hold tax deed sales?
- on application. Each sale is scheduled and advertised in advance, so check the county's tax deed calendar for the next posted date.
Tax Sale Atlas publishes educational information about public tax sale processes. This is not legal, financial, or investment advice. Rules, dates, and fees change; confirm with the county office before you bid.
Explore all 64 Colorado counties
Compare sale calendars, platforms, and rules across the state, or read the guides before you bid.