The Costilla County tax lien sale is an annual online auction where investors pay off other people’s delinquent property taxes in exchange for a certificate that earns interest at a statutory rate. You are not buying the property. You are buying the debt, and with it the right to collect that debt plus interest from the owner, or to pursue ownership through a separate process if the owner never pays.
The sale runs under Colorado statutes that apply to every county, but the Costilla County Treasurer sets the bidding rules, the fees, and the auction platform. What follows is how the process actually works, what it earns, and where the money quietly leaks out.
What You’re Actually Buying
When a property owner in Costilla County misses a tax payment, the Treasurer eventually puts a lien on that parcel up for auction. The winning bidder gets a certificate of purchase. The owner keeps the property and now owes you instead of the county.
Two things follow from that. If the owner pays, you get your money back with interest. If the owner never pays, you can apply for a Treasurer’s Deed after three years, but only through a separate legal process that has its own costs and its own auction step. The certificate itself is a debt instrument. Ownership is a different transaction that may or may not happen.
Registering and Researching Parcels
Costilla County runs the sale through an online auction platform.1Costilla County. Tax Lien Sale Information You create an account, submit identification, and provide a W-9 so the county can issue certificates in your name and report your interest income to the IRS.
Before you bid, look at what you would actually be lending against. The published delinquent list gives you a legal description and the total owed on each parcel. Legal descriptions are not addresses. Without a plat map or a GIS tool, you can end up with a lien on a landlocked slice of scrubland with no road access and no resale value. The county gives no warranties on any parcel: not on condition, not on access, not on whether structures exist, not on environmental history.
Some parcels on the list are marked “struck off” to the county, meaning they went unsold at a prior year’s auction. The fact that no one bid last time is information. Treat it that way.
How Bidding Works
Colorado uses a premium bidding system. Each lien starts at a base amount equal to the delinquent taxes, interest, and fees. Bidders compete by offering to pay more than that base. Whoever offers the largest premium wins the certificate.2Justia Law. Colorado Revised Statutes Section 39-11-115 – To Whom Tax Lien Shall Be Sold
Here is what new investors miss: the premium goes into the county general fund. It does not earn interest. You do not get it back when the owner redeems. Every dollar of premium you bid is a dollar of guaranteed sunk cost, and if you bid too much on parcels that redeem quickly, you can lose money on liens that technically “worked.”
The Treasurer sets the order in which liens are offered, the minimum bid increments, and any minimum thresholds. Those rules must be posted on the auction platform at least two weeks before the sale.2Justia Law. Colorado Revised Statutes Section 39-11-115 – To Whom Tax Lien Shall Be Sold Liens that draw no bids are struck off to the county.
Winning bidders usually have 24 to 48 hours to pay by ACH or wire. Miss that window and you forfeit the bid, and you may be barred from future sales.
Interest Rate and What It Applies To
The interest rate on a Colorado tax lien certificate is set each September 1 by the state Commissioner of Banking, using the Federal Reserve Bank of Kansas City’s discount rate plus nine percentage points, rounded to the nearest whole percent. The new rate takes effect October 1.3Justia Law. Colorado Revised Statutes Section 39-12-103 – Redemption Made – Interest For 2025, the rate is 14%. The 2026 rate will be set on September 1, 2026.
Interest accrues on the face value of the lien: the delinquent taxes, fees, and costs. It does not accrue on your premium. Partial months count as full months.3Justia Law. Colorado Revised Statutes Section 39-12-103 – Redemption Made – Interest
Endorsing Subsequent Taxes
If the same owner falls behind again the next year, you can add those new delinquent taxes to your existing certificate. This is called endorsing, or “subbing.” Investors typically do it in August, before the fall auction, which locks in two extra months of interest compared with waiting for the October sale.3Justia Law. Colorado Revised Statutes Section 39-12-103 – Redemption Made – Interest Endorsed amounts earn the same statutory rate. If you skip endorsement, another investor can pick up the new liens at the annual sale and complicate your later path to a deed.
If You’re the Property Owner
You do not lose your property at the tax lien sale. You keep ownership, and you have three years from the certificate’s issue date to redeem.4Justia Law. Colorado Revised Statutes Section 39-11-120 – Presentation of Certificates for Deed Redemption means paying the County Treasurer the full delinquent taxes, all accrued interest, any endorsed subsequent taxes with their interest, and the associated administrative fees.3Justia Law. Colorado Revised Statutes Section 39-12-103 – Redemption Made – Interest The Treasurer forwards the payment to the certificate holder.
You can redeem at any point before the Treasurer actually executes a deed, which means the window sometimes extends past the three-year mark if the certificate holder has not yet moved forward. That is not a plan. Interest keeps compounding every month, and once the formal notice period runs and the deed issues, your ownership ends.
Getting to a Treasurer’s Deed
Three years after the sale, if the lien is still unpaid, the certificate holder can apply for a Treasurer’s Deed. Costilla County charges a $1,200 non-refundable application fee as of July 1, 2025, to cover publication, service, and administrative costs.5Costilla County. Treasurer’s Deed Application
Before any deed issues, the Treasurer must notify everyone with a legal interest in the property, including occupants, the taxed owner, and anyone with a recorded interest like a mortgage lender. Notice goes out no less than three months and no more than five months before the deed can be issued, and for properties assessed at $500 or more it is also published in a local newspaper three times at one-week intervals.6Justia Law. Colorado Revised Statutes Section 39-11-128 – Condition Precedent to Deed – Notice
Colorado changed the deed process effective July 1, 2024. The Treasurer no longer issues a deed directly to the certificate holder. Costilla County now runs Treasurer’s Deed Auctions and posts upcoming dates on its website.7Costilla County. Upcoming Treasurers Deed Auctions The path from certificate to ownership now includes an additional auction step, and you should confirm current procedures with the Treasurer’s office before committing capital.
Costs That Show Up After the Deed
A Treasurer’s Deed is legal ownership. It is not marketable ownership. Title companies routinely refuse to insure tax deed titles, because prior owners, former lienholders, or parties with unrecorded interests may still have grounds to challenge the sale. To sell or borrow against the property, you will almost certainly need a quiet title action. Attorney fees for that typically run between $1,500 and $5,000, and the case can take several months.
If someone is living on the property, you also have to evict them through the normal court process. The deed does not remove occupants for you.
Environmental Liability Under CERCLA
Investors who acquire contaminated property through a tax deed can face federal cleanup liability under CERCLA, the Comprehensive Environmental Response, Compensation, and Liability Act. A federal appeals court has held that a tax sale creates a “contractual relationship” between the buyer and the property’s contamination history, which strips away the third-party defense that would otherwise protect an innocent purchaser. The lack of pre-sale access does not automatically shield you. Rural parcels with any history of mining, agricultural chemical storage, or dumping deserve extra caution.
Federal Tax Liens Don’t Automatically Disappear
A state tax lien sale does not wipe out a recorded federal tax lien. After a Treasurer’s Deed issues, the federal government keeps a right of redemption for 120 days or the period allowed under state law, whichever is longer.8Office of the Law Revision Counsel. 28 USC 2410 – Actions Affecting Property on Which United States Has Lien During that window the IRS can repay what you spent plus interest and take the property. Even if it doesn’t, many title insurers will not issue a policy until the redemption period expires. Check federal lien records before bidding.
Federal Income Tax on What You Earn
Interest paid on a redeemed lien is taxable income. When a property owner redeems, the county reports the interest to you and, if the total exceeds $10 in a calendar year, issues a Form 1099-INT. You report the interest whether or not the form arrives. The W-9 you submitted at registration is what ties the county’s report to your tax identification number, and failing to report interest the county already reported to the IRS is a straight path to an underreporting notice.
Premiums are not deductible as an investment expense in the year paid. Because a premium is non-refundable and earns no interest, it is a sunk cost that quietly reduces your effective return. Track your full outlay across the life of each certificate: original lien amount, premium, endorsed subsequent taxes, and, if it comes to that, the deed application fee. That is the only way to know whether the investment actually made you money.