Arapahoe County Property Tax: Deadlines, Exemptions, and Appeals

Arapahoe County property tax is calculated by multiplying your home’s assessed value by the combined mill levies of every taxing district that covers your address, and the Treasurer collects it in one payment due April 30 or in two installments due at the end of February and on June 15. Starting in 2025, Colorado applies two residential assessment rates rather than one, so the same home produces slightly different assessed values for the local-government and school-district portions of the bill.¹

How Your Bill Is Built

The Arapahoe County Assessor sets an actual (market) value for each property during every odd-numbered reappraisal year, using sales of comparable homes. For tax years 2025 and 2026, those sales must have closed between January 1, 2023, and June 30, 2024. When comparable sales in that 18-month window are thin, the Assessor can extend the data period backward in six-month increments up to five years before June 30, 2024.¹

The county then converts market value to assessed value using the two 2026 residential rates: 6.8% for local government purposes and 7.05% for school district purposes.¹ A home with an actual value of $500,000 carries a local-government assessed value of $34,000 and a school-district assessed value of $35,250.

Each district that overlaps your parcel — county, city, school district, fire, water and sanitation, and others — sets its own mill levy. One mill equals one dollar of tax per $1,000 of assessed value. Your bill is the sum of each district’s mill levy applied to the appropriate assessed value. The Assessor does not set mill levies; the individual districts do.

When and How to Pay

You can pay in full by April 30 or split the bill into two equal installments due by the last day of February and by June 15. If a due date lands on a weekend, payment must arrive or be postmarked by that date or the next business day.²

The Treasurer accepts several payment methods:

Online eCheck, free with no processing fee.
Online credit or debit card, with a percentage-based convenience fee charged by the payment vendor.
Mail, with a personal check payable to the Arapahoe County Treasurer and the payment coupon enclosed.
Drop box at the Administration Building in Littleton and Clerk and Recorder offices in Aurora, Centennial, and Byers. Payments must be deposited by noon on the due date to count as timely.
In person at the Treasurer’s office at 5334 S. Prince St., Littleton, which is the only location that accepts cash.³

If a mortgage servicer pays your taxes from escrow, federal law requires the servicer to pay on or before the deadline.⁴ If you think a payment was missed, contact both the servicer and the Treasurer, and you can send the servicer a formal notice of error.⁵

What Happens If You Pay Late

Delinquent taxes accrue interest at 1% per month, and partial months count as full months. Miss the February installment and interest on the first half starts March 1. Miss June 15 and interest on the second half runs from June 16. Miss April 30 on a full payment and interest applies to the entire balance from May 1.⁶

Unpaid balances lead to a tax lien. The Treasurer advertises delinquent properties and sells tax lien certificates at a public auction each fall. The buyer pays your tax debt and holds a lien against your property. To clear it, you must pay the original tax plus redemption interest, calculated by adding 9% to the Federal Reserve discount rate as of September 1 of the sale year. For certificates sold in late 2025, the redemption rate is 14% annually, roughly 1.17% per month.

If you fail to redeem within three years of the lien sale, the certificate holder can apply for a Treasurer’s Deed and take ownership of the property. Colorado law requires the holder to provide notice and meet research and notification requirements before that happens. A single year of unpaid taxes can start the process that eventually costs you the home.

Exemptions That Reduce the Taxable Value

Colorado offers three exemptions that reduce the taxable value of a qualifying homeowner’s primary residence. Each works the same way: 50% of the first $200,000 in actual value is exempt from taxation. On a $400,000 home, that removes $100,000 from the tax base. A property can only receive one exemption per year, even if the owner qualifies for more than one.⁷

Senior Exemption

You qualify if you are at least 65 on January 1 of the application year, you or your spouse are the owner of record, and you have owned and occupied the property as your primary residence for at least 10 consecutive years before January 1. The exemption must be applied for and funded in the state budget, and it has been funded continuously for many years.⁸

Disabled Veteran Exemption

Veterans with a 100% permanent disability rating from the U.S. Department of Veterans Affairs, or those granted individual unemployability status, qualify for the same 50% exemption on the first $200,000 of actual value. There is no 10-year ownership requirement. The veteran must be the owner of record and occupy the home as a primary residence as of January 1. If the veteran’s spouse owns the property, the veteran can still qualify as long as the couple was married and both lived in the home on January 1.⁹

Gold Star Spouse Exemption

The surviving spouse of a service member who died in the line of duty and received a Department of Defense death gratuity, or whose death resulted from a service-connected injury or disease, qualifies for the same exemption. The spouse must receive dependency and indemnity compensation from the VA. The ownership and primary-residence requirements match the disabled veteran exemption.¹⁰

Deferral for Seniors and Active Military

Separate from the exemptions, Colorado runs a property tax deferral program. It is not a discount. The state pays your property taxes, records a lien against your home, and charges interest on the deferred amount until repayment, which is typically triggered when the home is sold or the owner passes away.¹¹

To qualify, you must be 65 or older as of December 31 of the year you apply, own and occupy the home, have no delinquent property taxes, and carry total liens (including mortgages) that do not exceed the home’s actual value. Mortgage liens specifically cannot exceed 75% of the Assessor’s market value. Applications are filed between January 1 and April 1 each year, and participants must reapply annually, even in years they defer nothing new.

Protesting Your Valuation

Each May the Assessor mails a Notice of Valuation showing the market value assigned to your property. If the number looks too high, you can protest, and the evidence you bring is what moves the value.

The strongest protests use comparable sales: recent transactions of similar homes in your area that closed below the Assessor’s estimate. For the current cycle, those sales must have occurred between January 1, 2023, and June 30, 2024.¹ Sales outside that window generally will not count unless the Assessor used an extended data period.

Start by reviewing the property record in the Assessor’s online database. Errors in square footage, lot size, bedroom count, or condition ratings are common and inflate valuations. Deferred maintenance, structural issues, or other problems that comparable homes don’t share can be documented with photographs and contractor repair estimates.

Protests must be filed with the Assessor by June 8 of the valuation year, online, by mail postmarked by that date, or in person.¹² Keep the online confirmation, or mail certified with tracking. The Assessor must mail a Notice of Determination by July 10.¹³ If you disagree, you can appeal to the Arapahoe County Board of Equalization by written appeal postmarked or delivered no later than July 20. If the board’s decision still doesn’t satisfy you, you have 30 days from the mailed decision to appeal to the State Board of Assessment Appeals, a district court, or binding arbitration.

Deducting Property Taxes on Your Federal Return

Property taxes paid to Arapahoe County are deductible on your federal return if you itemize. The IRS allows a deduction for real estate taxes actually paid during the year, but not for water, sewer, or trash charges billed alongside the tax statement, and not for special assessments for local improvements such as sidewalks or streets.¹⁴

The deduction is subject to the state and local tax (SALT) cap. For the 2026 tax year, the cap is $40,000 for most filers with modified adjusted gross income below $500,000, and $20,000 for married taxpayers filing separately. Above $500,000 in income, the cap gradually decreases. Homeowners with high property tax bills may hit the ceiling and find the standard deduction more valuable than itemizing.

1
Colorado Department of Local Affairs Division of Property Taxation. Understanding Property Taxes in Colorado
2
Colorado General Assembly. HB25-1199 Property Tax Payment Schedule
3
Arapahoe County. Messages from Treasurer Michael Westerberg
4
Consumer Financial Protection Bureau. Escrow Accounts
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Consumer Financial Protection Bureau. What Should I Do If Im Having Problems With My Escrow or Impound Account
6
FindLaw. Colorado Revised Statutes Title 39 Taxation – 39-10-104.5
7
Colorado Department of Local Affairs Division of Property Taxation. Property Tax Exemption for Senior Citizens in Colorado
8
Colorado Department of Local Affairs Division of Property Taxation. Senior Property Tax Exemption
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Colorado Department of Local Affairs Division of Property Taxation. Property Tax Exemption for Veterans With a Disability and Gold Star Spouses
10
Colorado Division of Veterans Affairs. Property Tax Exemption
11
Colorado Property Tax Deferral Program. Colorado Property Tax Deferral Program
12
Colorado Department of Local Affairs Division of Property Taxation. Protests and Appeals
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Colorado Department of Local Affairs Division of Property Taxation. Filing Deadlines
14
Internal Revenue Service. Publication 530 Tax Information for Homeowners