When the sale is held
The auction must commence on or before the second Monday in December each year. If the lien cannot be advertised and offered by then, the treasurer holds the auction on a later date that still allows time for the required published notice. Most counties schedule the sale during the autumn, so confirm the exact date with the county treasurer.
When taxes go delinquent
Colorado property taxes may be paid in full or in two equal installments. The first installment is due by the last day of February and the second by June 15, or the full amount may be paid in a single payment by April 30. Delinquent interest runs at 1 percent per month from March 1 on a late first installment, from June 16 on a late second installment, and from May 1 on a late single payment. The treasurer must mail a delinquency notice to each owner no later than September 1, and the notice sets a payment date at least fifteen days out before the lien is advertised and sold. Parcels still unpaid go to the tax lien auction later that same year.
What happens after the sale
At least three years from the date of the tax lien sale, the lawful holder of the certificate of purchase may file an application with the treasurer for a public auction of a certificate of option for treasurer's deed. This is not a conventional tax deed sale of the parcel. What sells is the option to take the treasurer's deed, and the treasurer delivers the deed to the winning purchaser on demand once the property remains unredeemed. On and after July 1, 2024 this Article 11.5 process is mandatory and a treasurer may no longer issue a deed under Article 11, which is how Colorado answered Tyler v. Hennepin County on owner equity.
Leftover parcels between sales
If a tax lien draws no bid, the treasurer strikes it off to the county, city, town, or city and county for the taxes, delinquent interest, and fees, and issues that government a certificate of purchase. A county holding certificates of purchase may then assign, sell, or transfer them in the manner, at the times, and on the terms set by resolution of its board of county commissioners, which is the mechanism Colorado counties use to sell county-held liens over the counter between annual sales. A sale of a certificate on real estate that owes more than ten thousand dollars in taxes is not valid until the property tax administrator approves the sale and its terms after published notice. Availability, pricing, and whether a county offers a public list at all vary by county, so check with the treasurer.
These dates are the statewide statutory schedule. The exact auction date, registration deadline, and platform are set county by county, so confirm them on the Colorado county pages before you plan a bid. For the mechanics of the sale itself, see how to buy in Colorado.
Verified Jul 29, 2026 against Colorado statutes.
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.