Boulder County, CO
In-person premium-bid lien sale at the Boulder County Courthouse — registration from 7:30 a.m.
Boulder County still holds its tax lien sale in a room rather than online. The 2026 sale is on November 13 at the Boulder County Courthouse, 1325 Pearl Street, third floor. Registration opens at 7:30 a.m. that morning: bring your name exactly as it should appear on the certificates, an address for checks, your Social Security or tax ID number and a signed W-9. The auction starts as soon after 8:30 a.m. as everyone is registered and runs until every property is sold or 5 p.m.; in recent years it hasn't gone past 3 p.m. An auctioneer works through the list in the order it was published — alphabetical by owner — the bidding is open rather than rotating, and the amount you bid is the premium. Registered bidders get an eight-hour parking pass for four downtown city lots. Delinquent mobile home taxes aren't auctioned in Boulder County; they're struck off to the county.
Boulder publishes five years of results, and they show how the premium cuts into the return. At the 2025 sale (November 14), 25 investors turned up for 520 properties at a 14% rate, the average premium was 5.6%, and the sale collected $5,676,649.59 in taxes; in 2021 there were 42 investors for 402 properties at 9%, with a 7.5% average premium. The premium earns no interest, isn't returned and goes to the county's general fund, so the county's own example applies: a 6% premium on a lien paying 10% loses money if the owner redeems before eight months pass. The 2026 rate is 13% a year, calculated monthly. A Colorado tax lien is a first, prior and perpetual lien — only an earlier year's tax lien ranks ahead of it. The treasurer keeps the original certificates and mails copies within a week, and certificates can be sold on if they're notarized and recorded with the Clerk and Recorder.
Colorado rules at a glance
Colorado's rate is nine points above the federal discount rate, set each September 1 by the State Bank Commissioner (C.R.S. 39-12-103): 13% for liens sold from October 1, 2026. Bidders compete on a premium that goes to the county and earns no interest (C.R.S. 39-11-115). From August 1 of the third calendar year after the sale the holder can apply for a treasurer's deed, which now means a public auction (C.R.S. art. 11.5); the owner can redeem until seven days before it.
The statute, the bidding and what goes wrong for new buyers are on the Colorado page; every sale date we have sourced for Boulder County is on the Boulder County page.
Property & tax profile
The median homeowner in Boulder County pays $3,998 a year in property tax — above the Colorado median of $2,602 (U.S.: $3,119). That is roughly what a typical home here owes after one missed year — about the face value of a one-year certificate, before interest, fees and any premium. Homes with a mortgage pay a median of $4,010; homes owned outright, $3,977.
On a home with a mortgage, the lender has its own reason to pay a delinquent tax bill: the tax lien outranks the mortgage, and a tax deed can wipe out the loan. On a home owned outright, nobody but the owner — or the heirs — has that reason. In Boulder County, 33.9% of owner-occupied homes are owned outright (Colorado: 30.6%, U.S.: 39.4%). That is more than the state as a whole, so a larger share of the delinquent bills here have no lender behind them.
5.3% of all housing units in Boulder County are vacant. The figure that matters for a lien buyer is the Census “other vacant” category — not for rent, not for sale, not a holiday home, but a catch-all that includes foreclosures, homes held up by legal proceedings or family reasons, homes needing repairs, and abandoned ones. Here it is 1.2% of all units (Colorado: 1.7%, U.S.: 3.6%). That is below the state rate: fewer empty properties on the list than elsewhere in Colorado.
Half of the homes in Boulder County were built in or before 1986 (Colorado: in or before 1988). The typical tax bill is 3.8% of the median household income of $103,994 (Colorado: 2.7%).
Source: U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates (tables B25077, B25103, B25081, B25002, B25004, B25035, B19013) — see the figures on data.census.gov. Survey estimates with margins of error; anything too uncertain to state is left out.
Before you bid: The list of advertised properties and their status is updated each Friday on the treasurer's page, and owners who pay before the sale drop off it. Seating is limited — confirm registration, parking and the current list with the Boulder County Treasurer at 303-441-3520.
Official source: bouldercounty.gov — checked October 4, 2026
More sales: 38 other county sales are on the calendar in November 2026 — see them by date; or the upcoming sales in Colorado.
This page reflects publicly posted county auction notices as of publication and is general information, not financial or legal advice. Sale details can change — always confirm current terms with the county directly.