How Colorado income tax works

Colorado’s income tax return is built on top of the federal one. It does not ask you to list your wages, interest and pensions again. It takes one number from Form 1040, federal taxable income, and asks a series of questions about what Colorado treats differently. The answers are a short list of additions, a longer list of subtractions, a single multiplication at 4.40%, and a set of credits that are unlike anything on the federal return. The individual form is the DR 0104 (verify), and the additions and subtractions sit on a schedule behind it, the DR 0104AD.

That design has a consequence most people never think about: almost every federal decision flows through. Take the standard deduction federally, and Colorado starts from income after the standard deduction. Itemize, and Colorado starts from income after your itemized deductions, with one correction described below. The new federal deductions for tips, seniors and car loan interest reduce federal taxable income, so they reduce Colorado income too. The federal overtime deduction does not, because Colorado adds it back from 2026. Get the federal return right and most of the Colorado return is already right. Get it wrong and the error is taxed twice.

Who files

Full-year residents report everything, wherever it was earned, and take a credit for tax paid to another state on income taxed there too. Part-year residents, people who moved in or out during the year, report only the income earned while living in Colorado, split by date. Nonresidents who earned money here, from a Colorado rental, a Colorado job, or a business with Colorado customers, report only the Colorado-source share. All three use the same return; the part-year and nonresident versions add a schedule, the DR 0104PN, that works out the Colorado percentage. Married couples use the same filing status they used federally, and each spouse’s age-based subtractions are figured separately even on a joint return.

Where it starts: federal taxable income

Federal taxable income is the figure after adjustments, after the standard or itemized deductions, and after the deductions that sit outside both, such as the senior deduction. It is not adjusted gross income. The distinction matters because Colorado uses both numbers for different jobs. Taxable income is the starting point for the tax. Adjusted gross income, or AGI, is the yardstick for the tests: whether someone 55 to 64 is under the $75,000 or $95,000 line for the Social Security subtraction, whether the $300,000 deduction addback applies, and whether the income limits on the credits are met. Two returns with the same taxable income can be treated very differently in Colorado if their AGIs differ.

Because Colorado begins from federal taxable income, someone whose federal taxable income is zero generally has no Colorado tax, and in a year with no TABOR refund there may be nothing to claim either. But a return may still be worth filing for the refundable credits, or to get Colorado withholding back, and anyone who files a federal return should expect to file a Colorado one (verify filing threshold).

The additions

Colorado adds back a handful of things the federal return let you deduct or leave out. The common ones:

State income tax you deducted. If you itemized federally and your state and local tax deduction included Colorado income tax, that income tax comes back. Colorado will not let you deduct its own tax from its own tax base. Property tax is not added back; only the income tax portion is. With the SALT cap now at $40,400 and rising, more Colorado homeowners itemize again, and more of them have this addback.

Part of your federal deduction if AGI is $300,000 or more. Above that line most of the federal deduction is added back, and from 2026 nearly all of it: everything above $1,000 single or $2,000 joint. The rule, and why it falls hardest on charitable givers, is in Give it away, pay tax anyway.

Out-of-state municipal bond interest. Interest on bonds issued by other states and their cities is exempt from federal tax but taxable in Colorado. Colorado’s own bonds stay exempt. A brokerage statement that lumps all municipal interest together has to be split.

The federal overtime deduction, from 2026. The “no tax on overtime” deduction is added back on the Colorado return under HB25-1296. The tips deduction is not.

Smaller ones. Business meals above the 50% federal baseline, for 2024 through 2030. The qualified business income deduction, in full, for pass-through owners with AGI over $500,000 single or $1,000,000 joint; farmers are exempt.

The subtractions

The subtractions are where Colorado gives money back, and where returns prepared by people who do not know the state leave the most on the table. They go on Schedule DR 0104AD, and most of them have an age test, an income test, or a cap.

Social Security and retirement income. At 65 and older, all federally taxable Social Security comes off. From 55 to 64 it comes off if AGI is $75,000 or less single, $95,000 joint. Each person 65 or older can subtract up to $24,000 of pension, annuity, IRA and 401(k) income, and each person 55 to 64 up to $20,000, but the Social Security subtraction uses that cap first. The details, the examples and the 55-to-64 cliff are in Colorado for retirees.

529 contributions. Money put into a CollegeInvest 529 plan is subtracted, up to $26,200 per beneficiary for a single filer and $39,200 on a joint return for 2026. Grandparents and anyone else who contributes can take it; the account does not have to be theirs. This is one of the few state tax breaks available for saving rather than spending, and it is missed constantly because the federal return gives nothing for it, so nobody asks.

The rate

Take federal taxable income, add the additions, take off the subtractions, and the result is Colorado taxable income. Multiply by 4.40%. That is the tax. For a lot of retirees it is zero, as above. Larger IRA withdrawals, pensions and investment income are where Colorado tax starts.

The rate is flat but the tax is not always proportional. There are no brackets, no separate rate for capital gains, no local income tax on top. A $10,000 Roth conversion costs $440 of Colorado tax whether the taxpayer earns $30,000 or $300,000, which is why Colorado planning is less about timing and more about staying on the right side of the state’s few income lines.

The credits

This is the part of the Colorado return with no federal counterpart, and the part that changes most from year to year. Colorado’s credits for families are refundable: if the credit is bigger than the tax, the difference is paid out. Most of them are open to people who file with an ITIN, which the federal credits mostly are not. And several are tied to the state’s revenue, so they are larger in good years and smaller or absent in lean ones. For 2026 the state is in a lean year.

Earned income credit. Colorado pays a percentage of the federal earned income credit: 50% for 2025, 25% for 2026. Anyone who qualifies for the federal credit qualifies for the Colorado one, and the state version is also open to ITIN filers and some 18-to-24-year-olds without children (verify).

Child tax credit. A state credit for lower-income families with children under 6, separate from the federal $2,200 credit and refundable. For 2025 it was $1,200 per child if AGI was $26,000 or less single / $36,000 joint, $600 up to $51,000 / $61,000, and $200 up to $77,000 / $87,000 (verify 2026 amounts). The child does not need a Social Security number.

Child care credit. A share of the federal child and dependent care credit, growing to 70% of the federal credit for 2026, computed as if the federal credit were fully refundable, with the old low-income version folded in. Because the federal credit itself grew for 2026, the Colorado version grows twice over for families with child care bills.

Business owners. Owners of S corporations and partnerships can have the business elect Colorado’s pass-through entity tax. The business pays the Colorado tax, deducts it federally outside the SALT cap, and the owner takes a credit on the Colorado return for the tax the business paid. It has to be elected by the business, not the owner.

Other credits. The credit for tax paid to another state keeps a resident from being taxed twice on the same income. Credits for child care facility contributions, wildfire mitigation, enterprise zone activity, and a long list of narrower programs exist for the people they fit. What ended: the senior housing credit, up to $800, was for 2024 only.

The TABOR line

Near the bottom of the return is the state sales tax refund, which is how Colorado pays out the money it collected over its TABOR cap. It is a fixed amount per person, set by income tier (verify), paid to everyone who files, including people who owe nothing. For 2025 it was $19 to $59 a person. For 2026 the state’s revenue came in about $176 million under the cap, so the line is zero and there is no rate cut either. Software that carries last year’s refund forward will be wrong.

Withholding and estimated payments

Colorado tax is paid in during the year the same way federal tax is. Employers withhold it from wages and report it in the state boxes of the W-2. The state’s withholding tables are built around the 4.40% rate, so for a wage earner with no other income the withholding usually comes close. Rumors of a special 4.63% withholding rate on overtime for 2026 are false; there is no such rate.

Retirement income is different. Withholding on a pension or an IRA withdrawal is optional in Colorado (verify), and many payers withhold nothing for the state unless asked. A retiree who has federal withholding on an IRA at the default 10% may have no Colorado withholding at all, and then owes 4.40% of the taxable portion in April. The fix is a Colorado withholding election with the payer, or estimated payments.

Estimated payments go on Form DR 0104EP (verify) in four installments on the same dates as the federal ones, April 15, June 15, September 15 and January 15 (verify). They are required when the Colorado tax expected after withholding is more than $1,000 (verify), and the state charges an underpayment penalty figured quarter by quarter, much as the IRS does. The federal safe harbors, 90% of this year’s tax or 100% of last year’s, are mirrored in Colorado (verify).

How to file

Almost everyone files the Colorado return electronically with the federal one; the two go in together and the Colorado refund is deposited separately. The Department of Revenue’s site, tax.colorado.gov, hosts Revenue Online, where a taxpayer can check a refund, see a balance, make a payment, respond to a letter, and file some returns directly (verify). The due date is the same day as the federal return, and Colorado grants an automatic six-month extension to file, with no form, as long as at least 90% of the tax is paid by April 15 (verify). A Colorado return can generally be amended for four years after the due date, a year longer than the federal three.

What trips people up

• Social Security left in Colorado income, or the pension subtraction taken once for a couple instead of twice.
• The $24,000 stacked on top of Social Security instead of reduced by it.
• The gross pension or IRA amount used instead of the taxable amount.
• A 529 contribution nobody mentioned, because the federal return did not ask.
• The state income tax addback skipped by someone who itemized.
• Out-of-state municipal interest left out.
• Last year’s credits and TABOR refund carried into a year when they are off.
• A move-year return that gives Colorado a full year of a 1099-R instead of the months after the move.
• The extension taken as an extension to pay; penalties and interest run from April 15.