State estimated tax — 2026

Colorado Estimated Tax Payments 2026

Who has to make Colorado quarterly estimated payments, the 2026 due-date calendar, the safe-harbor rules that avoid an underpayment penalty, and how to pay through Revenue Online.

Who must pay

Colorado’s DR 0104EP requirement kicks in once your projected 2026 net Colorado tax, after withholding and credits are applied, tops $1,000.

2026 due-date calendar

Installment	% of annual estimate	Due date	Note
Q1	25%	April 15, 2026	—
Q2	25%	June 15, 2026	—
Q3	25%	September 15, 2026	—
Q4	25%	January 15, 2027	—

Colorado divides the required annual payment into four equal 25% installments — the due-date table in DR 0104EP moves any date landing on a weekend or legal holiday to the next business day.

Safe harbor — avoiding the underpayment penalty

Colorado’s required annual payment is the SMALLEST of the options you qualify for — and it does not use the 90% current-year test common elsewhere. The options are: 70% of your actual 2026 Colorado tax (always available; farmers and fishermen use 50% instead); 100% of your 2025 Colorado tax (only if you filed a full 12-month 2025 return AND your 2025 federal AGI was $150,000 or less, $75,000 or less married filing separately); or 110% of your 2025 Colorado tax (available with a filed 12-month 2025 return regardless of AGI). Above the $150,000/$75,000 AGI line, the 100% option disappears and you’re choosing between the 70% current-year test and the 110% prior-year test.

How to calculate your payment

Estimate your annual Colorado tax, test it against the safe harbor above, then split the required annual payment across the installments in the calendar. The site's quarterly planner handles the math and the federal side together.

Open the quarterly estimated tax calculator → Check your underpayment penalty exposure →

How to pay

Pay online through Revenue Online, or mail a check or money order with the Form DR 0104EP voucher. The DR 0104EP paper voucher is not required at all if you pay electronically through Revenue Online.

Penalty basics

Colorado charges interest on underpaid estimated tax under C.R.S. §39-21-109 and §39-21-110.5, at an annual rate the Department of Revenue publishes and adjusts each year. The published rate for 2026 is 11% (an 8% discounted rate applies in specified circumstances) — down from 12%/9% in 2025.

Colorado-specific notes

Colorado’s 70% current-year safe-harbor test is unusually low compared with the 90% test most other states use — but the trade-off is that the 100% prior-year option cuts off once your prior-year federal AGI exceeds $150,000 ($75,000 married filing separately), unlike states that just step the percentage up to 110% for everyone above a threshold.
Colorado’s flat rate moves under a TABOR-surplus "trigger": it was temporarily cut to 4.25% for tax year 2024 in a refund year, then reverted to 4.40% for 2025 and stays at 4.40% for 2026 — watch for a mid-cycle change if Colorado has another surplus year.
No DR 0104EP voucher is needed at all if every payment is made electronically through Revenue Online.

See the Colorado 2026 tax brackets for current rates, or the Colorado state tax calculator to estimate your full-year liability.

Frequently asked questions

When are Colorado estimated tax payments due in 2026?

The four Colorado due dates for 2026 are April 15, 2026, June 15, 2026, September 15, 2026, January 15, 2027. Colorado divides the required annual payment into four equal 25% installments — the due-date table in DR 0104EP moves any date landing on a weekend or legal holiday to the next business day.

Does Colorado use the same 90% safe-harbor test as most states?

No. Colorado’s current-year safe-harbor test is 70% of your actual 2026 tax (50% for farmers and fishermen), not the 90% used federally and in most other states. The trade-off is on the prior-year side: the 100% prior-year option only applies if your 2025 federal AGI was $150,000 or less ($75,000 or less married filing separately) — above that, your only prior-year option is 110%.

Could Colorado’s flat tax rate change again before 2026 is over?

It’s possible. Colorado’s income tax rate can be temporarily reduced under a TABOR-surplus "trigger" — it happened for tax year 2024, when the rate dropped from 4.40% to 4.25% before reverting. The rate is 4.40% for 2026 as things stand, but a large enough state revenue surplus could still trigger a reduction.

Do I need to mail a voucher if I pay Colorado estimated tax online?

No. If you pay every installment electronically through Revenue Online, you don’t need to file the paper DR 0104EP voucher at all — it’s only required alongside a check or money order payment.

How do I pay Colorado estimated tax?

Pay online through Revenue Online, or mail a check with the Form DR 0104EP voucher. The DR 0104EP paper voucher is not required at all if you pay electronically through Revenue Online.

Estimated tax in other states

Compare how Colorado stacks up against the other states with a Rising search trend for estimated-tax rules.