Adams County's September 15 Property Tax Deadline You Might Not Know About

by Rick Cavallaro

Adams County's September 15 Property Tax Deadline You Might Not Know About

Rhino Realty Pros gets asked about property taxes constantly, but this specific date catches even longtime Adams County homeowners off guard. Rick Cavallaro has started mentioning it proactively at closings, because it's brand new — most people paying property taxes directly, rather than through a mortgage escrow account, have never had this option before.

What Actually Changed

HB25-1199: The 4-Installment Payment Option

Starting with the 2025 property tax year (payable in 2026), Colorado created a new option letting eligible homeowners pay real property taxes in four equal installments instead of the traditional one or two lump-sum payments.

Colorado has historically given homeowners two ways to pay: in full by April 30, or in two installments, the first by the last day of February and the second by June 15. HB25-1199 added a third path — four smaller installments spread across the year — specifically to help homeowners who don't pay property taxes through a mortgage escrow account, including many retirees, seniors on fixed incomes, and owners with paid-off homes. AARP Colorado backed the change specifically because lump-sum or two-payment schedules can create real financial strain for homeowners living on a fixed monthly income.

Does Adams County Qualify?

Yes. The four-installment option is automatically available in any Colorado county with a population of 500,000 or more, based on the most recent census. Adams County's 2020 census population was 519,572, putting it over that threshold — meaning eligible Adams County homeowners have access to this option without needing any additional local approval.

The Full Schedule — and Why September 15 Matters

Installment	Due Date
1st installment	Last day of February
2nd installment	April 30
3rd installment	July 15
4th installment	September 15

If you're already using the 4-installment option this year, September 15 is your final payment — miss it, and delinquent interest starts accruing at 1% per month beginning September 16. If you're hearing about this option for the first time and missed enrolling by the April 30 checkpoint this year, this is the schedule to plan around for next year's tax bill instead. Worth noting too: the same legislation pushed back the notice-of-tax-lien deadline for delinquent property taxes from September 1 to October 15, giving homeowners who do fall behind a little more breathing room before a lien notice goes out.

Adams County Property Tax Installments — Quick Reference:
Who qualifies: Owners of residential or improved commercial property owing more than $25, not paid through a mortgage escrow.
Eligibility check: Must have paid at least half of taxes owed by April 30 to continue with installments 3 and 4.
Final installment: Due September 15 — 1%/month interest applies if missed.
Adams County status: Automatically eligible (population over 500,000).
Lien notice change: Delinquent tax lien notice deadline moved from Sept 1 to Oct 15.

Sources: Colorado General Assembly, HB25-1199 Property Tax Payment Schedule; AARP Colorado, "New Option for Paying Colorado Property Taxes"; Adams County Treasurer's Office, Due Dates & Delinquent Interest.

Why This Matters Beyond September

Most homeowners with a mortgage never think about property tax deadlines at all, since their lender handles it through escrow. But a meaningful number of Adams County owners — retirees, owners who paid off their mortgage, cash buyers — pay these bills directly, and for them, a single missed lump-sum payment can trigger real financial stress. If this is the first you're hearing about the 4-installment option, it's worth a call to the Adams County Treasurer's Office now to set it up correctly for next year's tax cycle, rather than defaulting back into the traditional one-or-two-payment schedule out of habit.

Frequently Asked Questions

What happens if I miss the September 15 property tax installment in Adams County?

If the fourth installment isn't paid by September 15, delinquent interest begins accruing on the unpaid balance at a rate of 1% per month starting September 16.

Who qualifies for Colorado's 4-installment property tax payment option?

Homeowners who owe more than $25 in property taxes on residential or improved commercial property, and whose taxes are not paid through a mortgage escrow account, are eligible, provided they pay at least half of the amount owed by April 30.

Is Adams County automatically part of the 4-installment program?

Yes. Counties with a population of 500,000 or more are automatically eligible, and Adams County's 2020 census population of 519,572 qualifies it without requiring separate local approval.

Why was this new payment option created?

The option was created primarily to help homeowners on fixed incomes, including many seniors and retirees, who pay property taxes directly rather than through a mortgage escrow account and could face financial strain from a single large lump-sum or two-installment payment.