Colorado Income Tax Calculator

Colorado's income tax system is one of the simplest in the country: a single flat rate of 4.4% applies to all taxable income, regardless of how much you earn. There are no graduated brackets, no income thresholds that trigger higher rates, and no complex phase-outs that make the calculation more difficult at higher income levels. Whether you earn $20,000 or $2 million in Colorado taxable income, every dollar is taxed at exactly the same 4.4% rate. This simplicity is a defining feature of Colorado's tax policy and makes paycheck withholding calculations straightforward for employers and employees alike.

The flat tax rate has been adjusted in recent years. Colorado's rate was 4.63% for many years before being reduced to 4.55% and then to 4.4% for tax year 2022 and beyond, reflecting the state's strong revenue position and TABOR surplus refund obligations. The Taxpayer's Bill of Rights (TABOR), which is embedded in Colorado's constitution, places limits on government revenue growth and requires excess revenue to be refunded to taxpayers — effectively providing a mechanism that can temporarily reduce the effective rate below 4.4% in years when the state over-collects. The 4.4% rate is set by statute and can be changed by the legislature within TABOR constraints.

Colorado's flat income tax applies to Colorado taxable income, which is derived from federal taxable income with a limited number of Colorado-specific additions and subtractions. Because federal taxable income is the starting point, the federal standard deduction, federal personal exemptions (historically, though they were eliminated in 2018 by the TCJA), and most common pre-tax deductions like 401(k) contributions and health insurance premiums automatically flow through to reduce Colorado taxable income as well. This conformity to the federal base makes Colorado one of the easiest states for tax professionals and individuals to calculate because most of the complexity is already resolved at the federal level.

Colorado does not have its own separate standard deduction. Instead, the state uses federal taxable income — the amount calculated after applying the federal standard deduction or itemized deductions — as its tax base. The 2024 federal standard deduction is $14,600 for single filers and $29,200 for married couples filing jointly, with additional amounts for taxpayers age 65 or older and for blindness. Because Colorado starts from federal taxable income, these federal standard deduction amounts effectively reduce your Colorado taxable income by the same amounts, even though Colorado itself does not publish a separate state standard deduction figure.

Colorado does make a small number of additions and subtractions from federal taxable income. Common subtractions include a subtraction for interest income on US government obligations (which is taxable federally but exempt in Colorado), a subtraction for military retirement income for qualifying veterans, and a subtraction for qualifying pension and annuity income for taxpayers over 55. Common additions include Colorado income taxes that were deducted as an itemized deduction on the federal return (a state conformity adjustment), and income from certain pass-through entity arrangements that receive special federal treatment. These adjustments are relatively minor for most wage earners.

Colorado's conformity to the federal income base means that changes in federal tax law directly affect Colorado revenue. The Tax Cuts and Jobs Act of 2017 increased the federal standard deduction significantly (from $6,500 to $12,000 for singles in 2018) and eliminated most itemized deductions for the majority of taxpayers. This change automatically reduced Colorado taxable incomes statewide because fewer Coloradans itemize and those who do have smaller deductions. The legislative response in Colorado was to reduce the flat tax rate from its previous level to partially offset the revenue windfall the state received from the broader federal taxable income base changes — demonstrating how closely Colorado's fiscal position is tied to federal tax policy.

The Taxpayer's Bill of Rights (TABOR) is a Colorado constitutional provision enacted in 1992 that limits state government revenue growth to the rate of inflation plus population growth each year. When Colorado collects more revenue than the TABOR limit allows, the excess must be refunded to taxpayers — it cannot be retained by the state for spending. These refunds are commonly called TABOR refunds or TABOR surplus refunds. In years when Colorado has significant TABOR refunds, the effective income tax rate experienced by taxpayers can be meaningfully below the statutory 4.4%, because a portion of the tax paid is returned through refund mechanisms.

TABOR refunds have been substantial in recent years as Colorado's economy grew faster than the inflation-plus-population formula anticipated. For tax year 2022, Colorado issued TABOR refunds of $750 per qualifying taxpayer regardless of income — a flat dollar amount that was particularly beneficial to lower- and middle-income filers as a percentage of their tax liability. For tax year 2023, additional TABOR refunds were distributed. These refunds are issued as direct payments or as a reduction of income tax owed when filing the Colorado return, depending on the mechanism chosen in a given year. The availability and amount of TABOR refunds varies significantly from year to year based on actual state revenues versus the TABOR limit.

Colorado has also used a temporary income tax rate reduction mechanism (rather than direct refunds) in some years to distribute TABOR surplus: the effective flat rate was reduced slightly below the statutory rate for an entire tax year, automatically lowering withholding and reducing year-end liability for all filers proportionally. This rate-reduction approach distributes the surplus more continuously throughout the year through lower withholding rather than as a lump-sum check after filing. When planning for Colorado income taxes, it is prudent to base projections on the statutory 4.4% rate and treat any TABOR refund as a positive but uncertain outcome, since the refund amount depends on actual state revenue performance against the TABOR cap.

Colorado requires a state income tax return from any resident of Colorado who is required to file a federal income tax return, any part-year resident who had income from Colorado sources while a resident, and any nonresident who had income from Colorado sources during the tax year. For full-year residents, the filing requirement mirrors the federal filing threshold: if you are required to file a federal return because your income exceeds the federal filing threshold (based on your filing status and age), you must also file a Colorado return. If you are not required to file federally, you generally are not required to file in Colorado either.

Part-year residents — individuals who moved to or from Colorado during the tax year — must file a Colorado return and pro-rate their income between the period of Colorado residency and the period of non-residency. Colorado uses a special computation that allocates income earned during the Colorado residency period to the Colorado tax base. Nonresidents who earn wages, business income, rental income, or other Colorado-source income must file a Colorado nonresident return. Colorado source income includes wages for work performed in Colorado, income from Colorado businesses, gains on Colorado real property, and income from Colorado-based pass-through entities.

Colorado residents may also be required to make quarterly estimated tax payments if they expect to owe more than $1,000 in Colorado income tax above their withholding and credits. Estimated payments are due on April 15, June 15, September 15, and January 15. For most W-2 employees with adequate employer withholding, estimated payments are not required. However, self-employed individuals, retirees with pension or investment income, landlords with rental income, and investors with significant capital gains commonly need to make quarterly Colorado estimated tax payments to avoid the Colorado underpayment of estimated tax penalty, which is assessed at a rate based on the federal underpayment rate.

Colorado residents and businesses with income not fully covered by employer withholding must make quarterly estimated tax payments to avoid penalties. The standard rule is that if you expect your Colorado tax after withholding to be $1,000 or more, you should make estimated payments. Colorado follows the same quarterly schedule as federal estimated taxes: payment 1 is due April 15 (covering January through March income), payment 2 is due June 15 (covering April and May), payment 3 is due September 15 (covering June through August), and payment 4 is due January 15 of the following year (covering September through December). Payments can be made online through Revenue Online, Colorado's tax portal, or by mail with Form DR 0104EP.

The safe harbor rule for avoiding Colorado underpayment penalties requires that your total payments — withholding plus estimated payments — equal at least 70% of your current-year Colorado tax liability, or 100% of last year's Colorado tax liability (whichever is less), applied in equal installments to each quarter. The 70% threshold is lower than the federal 90% safe harbor, making Colorado's estimated payment requirements somewhat more forgiving. Taxpayers with highly variable income — such as self-employed professionals with cyclical revenues, farmers, or investors with unpredictable capital gains — may choose to use the annualized income installment method to calculate each quarter's payment based on actual year-to-date income rather than making equal quarterly installments.

Colorado's Department of Revenue provides a Colorado Income Tax Withholding Worksheet (DR 0004) that employees can use to increase their employer withholding to cover income not subject to regular payroll withholding — such as self-employment income, rental income, or investment income. Increasing employer withholding throughout the year is often more convenient than making four separate estimated tax payments and reduces the risk of missing a quarterly deadline. For Colorado residents who receive TABOR refunds through a rate reduction mechanism built into withholding, the effective withholding rate may already be below 4.4% in those years, requiring careful monitoring to ensure total payments remain sufficient to meet the safe harbor threshold.