Capital Gains Tax on a Colorado House Sale: Exclusions & Rates

The capital gains tax on a Colorado house sale has two layers: the federal tax on any gain above the primary-residence exclusion, and Colorado’s flat 4.40% income tax on the same taxable portion.¹ A single filer can exclude up to $250,000 of gain on a primary residence and a married couple filing jointly can exclude up to $500,000, so many Colorado sellers owe nothing.² Anything above that threshold is taxed federally at 0%, 15%, or 20% based on your income, and then again by Colorado at 4.40%.

Figuring Out Your Gain

Your taxable gain is the net sale price minus your adjusted basis. Net sale price is what the buyer pays minus your selling costs: agent commissions, title fees, attorney fees, and any transfer taxes you cover. Your adjusted basis is what you originally paid for the home, plus the cost of every capital improvement you made over the years.³

Improvements Count, Repairs Don’t

Only capital improvements raise your basis and shrink your gain. An improvement adds value, extends the home’s useful life, or adapts it to a new use: a new roof, an added bathroom, central air, a finished basement, a new fence or driveway.⁴

Ordinary maintenance doesn’t count. Painting, patching cracks, fixing a leak, and replacing broken hardware are non-deductible repairs. One useful exception: when repair-type work is folded into a larger remodel, it rides along as part of the improvement. Replacing a single broken pane is a repair. Replacing every window as part of an energy overhaul is an improvement.⁴

Keep receipts and contractor invoices. The difference between a $100,000 gain and a $60,000 gain can be the $40,000 kitchen renovation you can’t document.

The $250,000 / $500,000 Primary-Residence Exclusion

Section 121 is the biggest break available to home sellers. Exclude up to $250,000 of gain as a single filer, or up to $500,000 married filing jointly. To qualify, during the five-year period ending on the sale date you must have owned the home for at least two years and lived in it as your primary residence for at least two years. Those two years don’t have to be consecutive.²

For a married couple to claim the full $500,000, both spouses must meet the use test, at least one must meet the ownership test, and neither can have used the exclusion on another home sale in the past two years.²

Because Colorado conforms to the federal treatment, any gain excluded under Section 121 is also excluded from your Colorado taxable income. If your entire gain fits inside the exclusion, you owe no state tax on the sale.

Partial Exclusion When You Sell Early

Sell before you’ve hit the full two years and you can still get a proportional exclusion if the sale was driven by a change in employment location, a health condition, or certain unforeseen circumstances. Qualifying events include divorce or legal separation, becoming eligible for unemployment compensation, the death of a spouse or co-owner, destruction or condemnation of the home, and multiple births from the same pregnancy.⁴

The partial exclusion is prorated by how much of the two years you actually met. Fifteen months of ownership and use with a qualifying job move gets you 15/24 of the full $250,000 or $500,000.

Federal Rate on the Leftover Gain

Gain above the exclusion is taxed at the federal long-term capital gains rate if you owned the home for more than a year. For 2026 the rates are 0%, 15%, or 20% depending on your total taxable income.⁵ The approximate 2026 thresholds:

0% rate: taxable income up to about $49,450 single, $98,900 joint, or $66,200 head of household.
15% rate: taxable income from those thresholds up to roughly $545,500 single, $613,700 joint, or $579,600 head of household.
20% rate: taxable income above those ceilings.

Most Colorado sellers with a taxable gain after the exclusion land in the 15% bracket. The 0% rate mostly reaches retirees or people with a low-income year; the 20% rate typically affects high earners only. Own the home a year or less and the gain is short-term, taxed at your ordinary income rate instead.

The 3.8% Net Investment Income Tax

Higher-income sellers face an additional 3.8% Net Investment Income Tax on the taxable portion of the gain. NIIT applies when your modified adjusted gross income tops $200,000 single, $250,000 joint, or $125,000 married filing separately. The tax hits the lesser of your net investment income or the amount your MAGI exceeds the threshold.⁶

An example: a single filer with $220,000 MAGI, including $100,000 of taxable gain after the Section 121 exclusion. MAGI exceeds $200,000 by $20,000, so NIIT applies to $20,000 — the lesser of the two figures — adding $760. NIIT is computed on Form 8960.

Colorado’s 4.40% on Top

Colorado taxes modified federal taxable income at a flat 4.40% for 2025, applied to all income types including capital gains.¹ The rate has moved recently — it was 4.25% for 2024 before reverting to 4.40% for 2025 — so confirm the rate for the year of your sale.

Only the gain that exceeds the federal exclusion feeds into your Colorado return. Colorado does have a capital gains subtraction, but for tax years 2022 and later it applies only to gains from Colorado agricultural land acquired between May 9, 1994 and June 4, 2009 and held at least five uninterrupted years.⁷ Residential property doesn’t qualify.

If You Depreciated Part of the Home

Claimed depreciation on a home office or a rented room? The Section 121 exclusion doesn’t cover the gain attributable to depreciation taken after May 6, 1997. That slice is taxed as unrecaptured Section 1250 gain at a maximum federal rate of 25%, even when the rest of your gain sits comfortably inside the exclusion.² Sellers who took a home office deduction for years without tracking the depreciation are the ones most often caught off guard.

Inherited and Gifted Homes

How you got the property changes the math. Inherit a home and your basis is generally the fair market value on the date the previous owner died — a stepped-up basis that wipes out decades of built-up appreciation.⁸ If the home was worth $450,000 when the owner passed and you sell for $475,000, your taxable gain is $25,000, not the swing from a purchase price decades earlier.

A gift is far less favorable. Your basis is the donor’s original basis: what they paid, plus their improvements. This carryover basis means you inherit their entire built-up gain.⁹ One wrinkle: if the fair market value at the time of the gift was lower than the donor’s basis, you must use the lower fair market value as your basis when calculating a loss. Ask the donor for purchase and improvement records before you sell.

Rental and Investment Property Sales

Section 121 doesn’t apply to a rental home, a vacation property, or any real estate you didn’t live in as a primary residence. The full gain is taxable, and there’s an added layer.

Depreciation you claimed on the rental is taxed at a maximum federal rate of 25% as unrecaptured Section 1250 gain.¹⁰ The remaining gain is taxed at the regular 0%/15%/20% long-term rate.⁵ Colorado then taxes the full gain at 4.40%, and NIIT can apply on top for higher earners.⁶ Stacked together, the effective rate on an investment property sale can approach half of the gain for a high-income seller.

A Section 1031 like-kind exchange defers the whole capital gains tax if you roll the proceeds into another investment property. The clock is strict: 45 calendar days from the sale to identify potential replacements in writing, and 180 calendar days to close.¹¹ A qualified intermediary must hold the proceeds; if you take the money in between, the exchange fails.

Reporting and Estimated Tax Payments

You must report the sale on your federal return if the closing agent issued a Form 1099-S, even when the entire gain is excludable. The closing agent can skip the 1099-S only if you certify in writing that the gain is fully excludable and the sale price is $250,000 or less ($500,000 for a certified married seller).¹²

Report on Form 8949, listing sale price, adjusted basis, gain, and the exclusion as a negative adjustment. Totals flow to Schedule D of your Form 1040. Seller-financed deals with at least one payment received in a later year use the installment method on Form 6252 instead.¹³

A large gain can blow past what your normal withholding covers. Expect to owe more than $1,000 in net Colorado tax for the year and you should make quarterly estimated payments to the Colorado Department of Revenue.¹⁴ The IRS has a matching $1,000 threshold. You can avoid the federal underpayment penalty by paying at least 90% of the current year’s tax or 100% of last year’s (110% if last year’s AGI was above $150,000).¹⁵ A $600,000 gain in a year you normally earn $120,000 won’t be covered by paycheck withholding. Sending an estimated payment shortly after closing is the simplest way to stay clean.

Selling as a Nonresident

Sell Colorado real property for more than $100,000 while living outside the state and Colorado requires withholding at closing. The amount is the lesser of 2% of the sale price or the net proceeds otherwise headed to you.¹⁶ The title company sends it to the Department of Revenue, and you claim it as a credit on your Colorado return, with any overpayment refunded. It’s a prepayment, not an extra tax, but it does reduce your check at closing.

1
Department of Revenue – Taxation. Individual Income Tax Guide
2
Office of the Law Revision Counsel. 26 USC 121 – Exclusion of Gain From Sale of Principal Residence
3
Internal Revenue Service. Property (Basis, Sale of Home, etc.) 3
4
Internal Revenue Service. Publication 523, Selling Your Home
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Internal Revenue Service. Topic No. 409, Capital Gains and Losses
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Internal Revenue Service. Topic No. 559, Net Investment Income Tax
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Colorado Department of Revenue. Income Tax Topics – Colorado Capital Gain Subtraction
8
Office of the Law Revision Counsel. 26 USC 1014 – Basis of Property Acquired From a Decedent
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Office of the Law Revision Counsel. 26 USC 1015 – Basis of Property Acquired by Gifts and Transfers in Trust
10
Office of the Law Revision Counsel. 26 USC 1 – Tax Imposed
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Office of the Law Revision Counsel. 26 USC 1031 – Exchange of Real Property Held for Productive Use or Investment
12
Internal Revenue Service. Instructions for Form 1099-S (04/2025)
13
Internal Revenue Service. Form 6252 – Installment Sale Income
14
Cornell Law Institute. Colorado Code 39-22-605 – Estimated Tax Penalty
15
Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty
16
Colorado Department of Revenue. FYI Income 5 – Nonresident Real Estate Transactions – Required Withholding