How Home Improvement Capital Expenditures Affect Your Taxes

Money you spend on qualifying home improvements gets added to your home’s tax basis, and a higher basis means a smaller taxable gain when you sell. That is how home improvements and capital gains tax connect: every documented improvement quietly shrinks the profit the IRS can tax, and for sellers whose gain runs past the federal exclusion of $250,000 for single filers or $500,000 for married couples filing jointly, that shrinkage is the difference between a large tax bill and none at all.¹

How the Math Actually Works at Sale

When you sell your primary residence, the IRS calculates your gain by subtracting your adjusted basis from the sale price. Your adjusted basis starts with what you paid for the home, including purchase closing costs, and grows every time you make a qualifying capital improvement. Casualty loss deductions, insurance reimbursements for damage, and any depreciation claimed if you used part of the home for business reduce basis in the other direction.²

Selling expenses also cut the taxable gain, though on the other side of the equation: real estate commissions, legal fees, advertising, title insurance, and loan charges you paid on the buyer’s behalf come off the sale price before the gain is calculated.³

To use the Section 121 exclusion at all, you need to have owned and lived in the home for at least two of the five years before the sale, and you can’t have claimed the exclusion on another home sale in the prior two years.¹ Surviving spouses selling within two years of a spouse’s death may still qualify for the full $500,000.

A quick illustration: buy for $300,000, add $80,000 in documented improvements, sell for $700,000. Your gain is $320,000 instead of $400,000. For a single filer with the $250,000 exclusion, that shifts the taxable amount from $150,000 down to $70,000. Long-term capital gains rates in 2026 range from 0% to 20% depending on income, so the dollars saved by tracking improvements accurately are real and often large.

What Counts as a Capital Improvement

The IRS defines a capital improvement as work that adds to the home’s value, prolongs its useful life, or adapts it to a new use, with a useful life of at least one year when installed.³ Federal tax law bars you from deducting these costs as current expenses; the trade-off is that they get added to basis instead.⁴

Publication 523 groups qualifying projects by category:

Additions: bedrooms, bathrooms, decks, garages, porches, patios.
Lawn and grounds: landscaping, driveways, walkways, fences, retaining walls, swimming pools.
Systems: heating, central air conditioning, duct work, security systems, wiring upgrades, central vacuum, lawn sprinklers.
Exterior: new roofing, siding, storm windows, storm doors, satellite dishes.
Insulation: attic, wall, floor, pipe or duct.
Plumbing: septic systems, water heaters, water softeners, filtration systems.
Interior: built-in appliances, kitchen modernization, permanent flooring, wall-to-wall carpeting, fireplaces.

The common thread is permanence. These projects physically alter the home’s structure or systems and stay with the property when it changes hands. Building permit fees, architect’s fees, and contractor payments tied to a qualifying improvement all count as part of its cost.⁵

What Doesn’t Count

Routine upkeep that keeps the home functional without making it more valuable or longer-lasting is not a capital improvement. Three categories are explicitly excluded:

Repairs and maintenance: painting inside or out, fixing leaks, filling holes or cracks, replacing broken hardware.
Improvements no longer present: if you installed wall-to-wall carpeting years ago and later tore it out, the old carpeting no longer counts toward basis.
Short-lived improvements: anything with a life expectancy of less than one year when installed.

This distinction trips up homeowners more than any other. Replacing one broken window pane is a repair. Replacing every window in the house with energy-efficient models is an improvement. Patching a roof leak is maintenance. Installing an entirely new roof is a capital expenditure.³ If a project restores the home to its existing condition without making it better or longer-lasting, treat it as a repair.

Energy Improvements: Basis and a Separate Credit

Certain energy-efficient upgrades do double duty. The full cost still gets added to your basis as a capital improvement, and the same spending may separately qualify for a federal tax credit that directly reduces the tax you owe in the year of installation.

The Energy Efficient Home Improvement Credit under Section 25C covers items like insulation, windows, doors, and efficient heating and cooling equipment at 30% of cost, subject to annual caps (a $1,200 general limit, with a separate $2,000 allowance for heat pumps and biomass stoves).⁶ The Residential Clean Energy Credit under Section 25D covers solar, solar water heaters, geothermal heat pumps, and battery storage at 30% with no annual dollar cap for systems placed in service through the end of 2032.⁷ Claiming a credit does not stop the same spending from raising your basis; both work in parallel.

If You Inherited or Received the Home as a Gift

Not every homeowner started with a purchase price, and the starting number changes the entire capital gains picture.

For an inherited home, your starting basis is generally the fair market value on the date the previous owner died, not what they originally paid. This stepped-up basis can dramatically reduce or eliminate taxable gain. An executor may instead elect an alternate valuation date if a federal estate tax return is filed.⁸ Any improvements you make after inheriting are added on top of that stepped-up figure.

Gifts work differently. Your basis is generally the donor’s adjusted basis at the time of the gift, so you inherit their cost history rather than the current market value. If the fair market value at the time of the gift was lower than the donor’s basis, a split-basis rule applies: the donor’s basis is used to calculate gains, but the lower fair market value is used to calculate losses. A portion of any gift tax the donor paid on the transfer may also add to your basis.⁵

Medical Modifications Follow Different Rules

Home modifications driven by a medical need aren’t simply basis items. They can qualify as deductible medical expenses in the year you pay for them, which is a separate track from the capital gains calculation. Publication 502 lists accessibility modifications that typically don’t raise a home’s market value and can therefore be deducted in full, including entrance and exit ramps, widened doorways and hallways, bathroom grab bars and railings, lowered cabinets, porch lifts, and modifications to stairways, fire alarms, and door hardware.⁹

When a medical improvement does raise the home’s value, you can only deduct the difference between the cost and the value increase. If the improvement costs $8,000 and the home’s value rises by $4,400, the deductible medical expense is $3,600. When the value increase equals or exceeds the cost, there is no medical deduction, but the improvement still raises your basis for capital gains purposes. The deduction is also only usable to the extent your medical expenses exceed 7.5% of adjusted gross income, and only if you itemize on Schedule A.¹⁰

The Records That Make It Real

A basis increase is only worth what you can prove. The IRS expects homeowners to keep records supporting every basis adjustment for as long as they own the property, and for at least three years after filing the return that reports the sale.¹¹ For a home you hold 25 years, that’s nearly three decades of files.

For each project, keep:

Original receipts and invoices for materials and labor.
Cancelled checks or credit card statements confirming payment.
Signed contracts specifying scope and price.
Contractor name and contact information.
The completion date.
Building permits and inspection records where applicable.

A simple spreadsheet listing every project by date, description, and total cost makes the basis calculation painless when you eventually sell. Digital copies of paper records are cheap insurance against loss.

If records are already gone, you can still rebuild. Contractors can issue written statements confirming past work and cost. Banks and credit card companies keep historical statements. Home equity lenders retain records of what was financed. Appraisals from mortgage refinances, insurance policy valuations, and even photographs that happen to show improvements can back up your figures.¹² For inherited property, probate records and the estate attorney’s files often contain the appraisal that fixes your starting basis. Reconstructing after the fact is always harder than keeping records as you go, and homeowners who try to piece together twenty years of history at the closing table usually leave money behind.

1
Office of the Law Revision Counsel. 26 USC 121 – Exclusion of Gain From Sale of Principal Residence
2
Office of the Law Revision Counsel. 26 USC 1016 – Adjustments to Basis
3
Internal Revenue Service. Publication 523, Selling Your Home
4
Office of the Law Revision Counsel. 26 USC 263 – Capital Expenditures
5
Internal Revenue Service. Publication 551, Basis of Assets
6
Office of the Law Revision Counsel. 26 USC 25C – Energy Efficient Home Improvement Credit
7
Office of the Law Revision Counsel. 26 USC 25D – Residential Clean Energy Credit
8
Internal Revenue Service. Gifts and Inheritances
9
Internal Revenue Service. Publication 502, Medical and Dental Expenses
10
Internal Revenue Service. Topic No. 502, Medical and Dental Expenses
11
Internal Revenue Service. Publication 530, Tax Information for Homeowners
12
Internal Revenue Service. Reconstructing Records After a Natural Disaster or Casualty Loss