Indexation Tax on Property: U.S. Rules, Section 121, and 1031 Exchanges

The indexation tax treatment many property owners hope for does not exist in the United States: federal law does not adjust your purchase price for inflation, so capital gains tax applies to the full nominal difference between what you paid and what you sold for. If you bought a home for $200,000 and sell it for $500,000, the IRS treats the entire $300,000 as your gain, even though much of that increase just reflects decades of rising prices. What the tax code offers instead is a set of provisions that can shrink or eliminate the taxable portion: basis adjustments for improvements, the Section 121 primary residence exclusion, preferential long-term rates, and 1031 like-kind exchanges for investment property. Used together, they are the reason most home sellers pay far less than the headline gain suggests.

Why U.S. Law Has No Inflation Adjustment for Property

Indexation, where it exists in other countries, increases the original purchase price of an asset to reflect inflation before the gain is calculated. A $1,000 asset bought in 2005 and sold today for $5,000 would have its basis lifted to roughly $1,600, cutting the taxable gain from $4,000 to $3,400.¹ The United States has never adopted that mechanism for capital gains.

Bills to change this, including the Capital Gains Inflation Relief Act, have been introduced in Congress, and some administrations have looked at whether Treasury could index by regulation without new legislation.² None have become law. Until that changes, every dollar of nominal appreciation on a property sale is potentially taxable, and the provisions below are your only levers for reducing the bill.

How the Gain Is Calculated

The formula is subtraction: sale price minus your adjusted basis equals your capital gain. Basis begins as the original purchase price plus closing costs paid at acquisition. Federal law then requires you to increase it for qualifying capital improvements and decrease it for any depreciation you claimed or were entitled to claim.³

A property bought for $300,000, improved with $50,000 in qualifying work, and sold for $500,000 has an adjusted basis of $350,000 and a taxable gain of $150,000. That number is the starting point for every rate and exclusion described below. Getting basis right matters more than any other single step: every dollar added to basis is a dollar removed from the taxable gain.

Adding Improvements to Basis: The Closest Substitute for Indexation

Because you cannot lift the purchase price for inflation, the practical alternative is capturing every qualifying dollar of investment in the property. The IRS separates improvements from repairs. Improvements add value, extend the property’s useful life, or adapt it to new uses, and they increase basis. Repairs keep the property in working order and do not.

Improvements that qualify include:⁴

Additions such as bedrooms, bathrooms, decks, garages, and porches
Systems such as central air conditioning, heating, security systems, and wiring upgrades
Exterior work including new roofs, siding, and storm windows
Interior work such as kitchen modernization, built-in appliances, flooring, and fireplaces
Lawn and grounds work including landscaping, driveways, fences, retaining walls, and swimming pools
Insulation in attics, walls, floors, and pipes

Painting a room, patching a crack, or fixing a leaky faucet does not count. One exception matters: a repair done as part of a larger renovation counts as an improvement. Replacing one broken window is a repair; replacing that window as part of a whole-house window project is an improvement.⁴ Keep receipts for every project. Years later, those records translate directly into a lower tax bill.

Section 121: The Primary Residence Exclusion

For homeowners, the most valuable provision in the code is Section 121, which excludes up to $250,000 of gain if you file as a single taxpayer, or up to $500,000 if you file jointly with your spouse.⁵ For a large share of home sales, this exclusion erases the federal capital gains tax entirely.

To qualify, you must meet two tests during the five-year period ending on the sale date:⁶

Ownership: you or your spouse owned the home for at least two of the previous five years
Use: you and your spouse each used the home as your primary residence for at least two of the previous five years

The two years do not have to be consecutive. You also cannot have excluded gain from another home sale in the two years before the current one.⁶ For joint filers, either spouse can meet the ownership test, but both must independently meet the use test. Boundary worth noting: this exclusion is for a principal residence. Second homes and pure investment properties do not qualify.

1031 Exchanges for Investment Property

Investment and business property has its own deferral tool. A Section 1031 like-kind exchange lets you sell one investment property and roll the proceeds into a replacement of equal or greater value without recognizing gain at the time of sale. The tax is deferred rather than forgiven; it comes due whenever you eventually sell out without doing another exchange.

The deadlines are strict. You have 45 days from the sale of the original property to identify potential replacements, and the exchange must close within 180 days of the sale or by the due date of your tax return for that year, whichever comes first.⁷ All proceeds must be held by a qualified intermediary during the process; the moment you take possession of the money, the transaction becomes taxable.

Primary residences and second homes used mainly for personal purposes do not qualify. The property must be held for business or investment use. Stocks, bonds, partnership interests, and property outside the United States are also ineligible. Some investors chain exchanges throughout their lifetime and pass the property to heirs, who receive a stepped-up basis that can eliminate the deferred gain.

What You Actually Pay on the Remaining Gain

Whatever gain remains after basis adjustments and exclusions runs through the rate structure. Hold the property more than one year and it qualifies for long-term capital gains rates. Sell in a year or less and the gain is short-term, taxed at your ordinary income rate, which reaches 37% at the top bracket. The IRS counts the holding period from the day after acquisition through the day of sale, so missing the one-year mark by a single day converts the entire gain to ordinary income.⁸

Long-term rates for 2026 are graduated by taxable income and filing status:⁹

0% on taxable income up to $49,450 (single), $98,900 (married filing jointly), or $66,200 (head of household)
15% from those thresholds up to $545,500 (single), $613,700 (married filing jointly), or $579,600 (head of household)
20% above those upper thresholds

Most sellers land in the 15% band, but a large property gain can push you into 20% for the year of the sale even if your regular income is modest.

The 3.8% Net Investment Income Tax

Higher-income sellers pay an additional 3.8% surtax on net investment income when modified adjusted gross income exceeds $200,000 (single), $250,000 (married filing jointly), or $125,000 (married filing separately).¹⁰ These thresholds are not indexed for inflation, so the surtax reaches more taxpayers each year. The 3.8% applies to the lesser of net investment income or the amount of MAGI over the threshold.

Depreciation Recapture on Rentals

If you claimed depreciation on a rental or investment property, that portion of the gain is taxed separately. Unrecaptured Section 1250 gain, covering depreciation on the building itself, is taxed at a maximum rate of 25%.⁸ Depreciation on personal property items identified through cost segregation (appliances, carpeting, certain fixtures) is recaptured as ordinary income at your marginal rate. Because the IRS reduces basis by depreciation “allowed or allowable,” recapture is owed even on deductions you never actually took.

Reporting the Sale

Every property sale is reportable, even one where the gain is fully excluded under Section 121. The transaction goes on Form 8949 and the totals flow to Schedule D of Form 1040. If the closing agent issued a Form 1099-S showing the gross proceeds, the IRS already has the number. For an excluded home sale, list the transaction on Form 8949 and use code “H” to enter the excluded gain as a negative adjustment, bringing the reportable amount to zero.¹¹ Rental and investment sales with depreciation recapture also require Form 4797. Underreporting or omitting a sale draws late-filing, late-payment, and accuracy-related penalties, plus interest; because the 1099-S is already in the IRS system, mismatches are among the easier ones to catch.¹²

1
The Budget Lab. Indexing Capital Gains to Inflation
2
Congress.gov. Indexing Capital Gains Taxes for Inflation
3
Office of the Law Revision Counsel. 26 US Code 1011 – Adjusted Basis for Determining Gain or Loss
4
Internal Revenue Service. Publication 523, Selling Your Home
5
Office of the Law Revision Counsel. 26 USC 121 – Exclusion of Gain From Sale of Principal Residence
6
Internal Revenue Service. Sale of Your Home
7
Internal Revenue Service. Like-Kind Exchanges Under IRC Section 1031
8
Internal Revenue Service. Topic No 409, Capital Gains and Losses
9
Tax Foundation. 2026 Tax Brackets and Federal Income Tax Rates
10
Office of the Law Revision Counsel. 26 USC 1411 – Imposition of Tax
11
Internal Revenue Service. Instructions for Form 8949
12
Internal Revenue Service. Avoiding Penalties and the Tax Gap