Colorado Paycheck Tax Calculator (2026 Flat 4.4%)

Colorado keeps its income tax deliberately simple: a flat 4.4% applied to federal taxable income with a short list of state additions and subtractions. Because the starting point is federal taxable income, your federal standard or itemized deduction already reduces the Colorado base, which makes Colorado’s effective rate lower than a naive 4.4%-of-income estimate suggests.

Colorado is a major locum tenens and travel-professional market, from mountain-town emergency coverage to Front Range hospital systems. For a physician based in Colorado, the flat 4.4% is the home layer; assignments elsewhere generate nonresident filings with a Colorado credit capped at 4.4%. For out-of-state physicians working Colorado assignments, Colorado taxes the income earned here on a nonresident return.

The calculator above applies the flat rate. The distinctive Colorado wrinkle worth understanding is TABOR, which can change the rate itself in surplus years.

Colorado starts from federal taxable income, so the 2026 federal standard deduction ($16,100 single, $32,200 married filing jointly per Rev. Proc. 2025-32) already carves down the state base before the 4.4% applies. A single wage earner making $200,000 with only the standard deduction has Colorado taxable income around $183,900 and state tax near $8,092, an effective rate of roughly 4% on gross wages.

State modifications adjust the base in both directions: additions for items like non-Colorado municipal bond interest, and subtractions including a retirement income exclusion for older taxpayers. But for most working households, federal taxable income times 4.4% is very close to the final number. One consequence worth noting: because the base is federal, anything that lowers federal taxable income, 401(k) deferrals, HSA contributions, itemized deductions, automatically lowers Colorado tax too, at 4.4 cents per dollar.

Colorado is one of the few states where the state withholding certificate, Form DR 0004, is optional. If you never file one, your employer derives Colorado withholding from your federal W-4. That default works well for single-income W-2 households, and poorly for the usual suspects: dual high incomes, large 1099 or investment income, and anyone whose federal W-4 carries adjustments that should not proportionally flow to the state.

Supplemental wages such as bonuses are withheld at the flat 4.4%, which exactly matches the real rate, so Colorado bonus withholding is self-correcting in a way graduated states are not. Underwithholding risk therefore concentrates entirely in income that has no withholding: locum 1099 pay, K-1 income, and gains, which need quarterly estimated payments.

One small local footnote: a few Colorado cities charge flat-dollar occupational privilege taxes on people who work there, a few dollars per month split with the employer. They appear as tiny paycheck lines, require no employee filing, and are not income taxes in any planning sense; Colorado has no municipal wage income taxes to model.

Colorado has no reciprocity agreements with any state. A Colorado-based locum physician files a nonresident return in every taxing assignment state and claims a Colorado credit for tax properly paid there, capped at Colorado’s 4.4% on the same income. Assignments in higher-rate states cost the excess above 4.4%; assignments in no-tax states (Wyoming next door, Texas, Florida) simply pay Colorado.

Out-of-state physicians taking Colorado assignments owe Colorado nonresident tax on Colorado-source income at the same flat rate, and their home state’s credit rules determine the net cost. Agencies typically do not withhold Colorado tax on 1099 pay, so quarterly estimates to Colorado are the physician’s job.

The federal tax-home rules do the heavy lifting on deductibility: maintaining a Colorado tax home while taking temporary assignments (a year or less) keeps travel, lodging, and meals deductible on 1099 work. Mountain-town assignments that quietly renew toward permanence are the classic way that status gets lost.

Two assignments, same $90,000 fee, different outcomes. Worked in Wyoming: no assignment-state tax, no nonresident return, and Colorado collects its 4.4%, about $3,960. Worked in Illinois: Illinois takes 4.95% on a nonresident return, about $4,455, and the Colorado credit stops at the $3,960 Colorado would have charged, so roughly $495 of Illinois tax is unrecoverable and the total state cost rises to $4,455. The Wyoming contract nets about $495 more on identical terms, before even counting the second filing. Small per contract, but across a locum year of rotating states it compounds into real money and real filing volume.

Among the states our calculators cover, Colorado’s 4.4% lands mid-pack: above North Carolina (3.99%), Pennsylvania (3.07%), and Ohio (2.75%), below Illinois (4.95%) and Georgia (4.99%), and far below the graduated coastal states. Regionally, the sharper contrasts are Wyoming with no income tax to the north and New Mexico and Utah with their own structures south and west, which is exactly the arbitrage a mobile physician can price into assignment choices.

Colorado also has no local income taxes on wages worth planning around, and its property taxes are among the lowest effective rates in the country at roughly 0.49% on owner-occupied homes per 2023 Tax Foundation data, a meaningful offset in the all-in cost of a Colorado base despite high home prices.

A single-employer W-2 household living and working in Colorado is close to fully served by defaults: federal-linked withholding, a flat rate, bonus withholding that matches the real rate, and no local layer. Planning value concentrates with multi-state clinicians and consultants, households with large unwithheld income, new arrivals with trailing income from a former state, and anyone deciding between a Colorado base and a no-tax neighbor.

Projection candidates from a Colorado base cluster in four groups. Rotating locum physicians whose assignment mix spans no-tax Wyoming, flat-tax neighbors, and graduated coastal states, each with its own estimate schedule and credit cap. Travel nurses and clinicians relying on stipends, where the tax-home documentation decides whether five figures of housing money is taxable. Remote employees of California or New York companies who moved to Colorado with equity still vesting, carrying old-state allocations for years. And dual-income households whose federal-W-4-derived state withholding has never been checked against the actual joint picture.

A realistic scenario: a Denver-based emergency physician earns $150,000 W-2 at a Front Range hospital plus $130,000 of 1099 assignments split between Casper, Wyoming and a California coastal hospital. The projection sets aside 4.4% on the Wyoming income (Colorado only), runs the California nonresident math at graduated rates with a Colorado credit capped at 4.4%, schedules quarterly estimates to two states on different calendars, verifies the stipend arrangement against her tax-home facts, and decides whether a DR 0004 additional-withholding election can replace the Colorado estimates entirely. That is an afternoon of planning that repriced both contracts.