A couple in Denver who bought their house for $180,000 in 1998 could sell it for north of $650,000 today, based on Colorado’s FHFA House Price Index trajectory. That is a gain of roughly $470,000 before adjustments. If they file jointly, the federal exclusion covers $500,000, so they would likely clear the threshold. But a single filer in the same house, perhaps a widow or a divorced owner, would face a taxable gain of more than $200,000 above the $250,000 cap. The federal tax bill on that overage could easily exceed $30,000, plus whatever the state charges.
This is not a scenario limited to mansions or investment properties. It is happening to people who simply stayed in their homes, paid their mortgages, and watched the neighborhood appreciate. The reason: the capital gains exclusion for primary-residence sales has been frozen at the same dollar amounts since Congress created it in 1997, and nearly three decades of rising home prices have quietly turned a generous tax break into a narrowing one.
How the exclusion works
Section 121 of the Internal Revenue Code allows homeowners to exclude up to $250,000 of gain on the sale of a principal residence ($500,000 for married couples filing jointly) from federal income tax. To qualify, the seller must have owned and lived in the home as a primary residence for at least two of the five years before the sale. The exclusion can be used only once every two years. A special provision extends the $500,000 threshold to certain surviving spouses who sell within a limited window after a spouse’s death.
When Congress set those figures in the Taxpayer Relief Act of 1997, the national median existing-home price was about $128,000, according to historical data from the National Association of Realtors. The exclusion was deliberately generous: $250,000 covered nearly double the median price, and $500,000 was almost four times the median. For the vast majority of sellers, the entire gain on a primary residence was sheltered.
Why the math no longer works for many sellers
Unlike most other key figures in the tax code, the Section 121 exclusion amounts are not indexed to inflation. Testimony submitted to the Senate Finance Committee has noted this gap explicitly, pointing out that the thresholds lack any adjustment mechanism. Had the $250,000 single-filer exclusion been indexed to the Consumer Price Index since 1997, it would stand at roughly $485,000 in 2025 dollars. The married-couple exclusion would be approaching $970,000.
Meanwhile, home values have surged. The FHFA’s national House Price Index shows that nominal prices nationwide have more than tripled since 1997. In high-appreciation metros, the gains are even steeper. Markets in parts of California, the Pacific Northwest, Colorado, and the Northeast corridor have seen values climb four or five times over that span. A homeowner who bought at $200,000 in one of those areas and sells at $800,000 or more is looking at a gain that blows past even the joint-filer exclusion.
The result is that a tax provision designed to make home sales painless for ordinary families now catches a growing slice of them. Long-tenured homeowners, retirees looking to downsize, and single filers (including widows and widowers past the special filing window) are the most exposed.
What sellers actually owe
Any gain above the exclusion limit is taxed as a long-term capital gain, assuming the seller owned the home for more than a year. As of the 2025 tax year, federal long-term capital gains rates are 0%, 15%, or 20%, depending on taxable income. High earners may also owe the 3.8% Net Investment Income Tax, bringing the top effective federal rate to 23.8%. State income taxes, where applicable, stack on top of that.
The IRS walks sellers through the calculation in Publication 523. The starting point is the sale price minus the seller’s “basis” in the home. Basis is generally the original purchase price plus certain closing costs paid at acquisition, plus the cost of qualifying capital improvements made over the years (a new roof, a kitchen renovation, an addition), minus any depreciation claimed for business or rental use of part of the property after May 6, 1997. The higher the basis, the smaller the taxable gain.
Sellers who receive Form 1099-S from their closing agent must report the transaction on their federal return even if no tax is owed, according to IRS guidance on home-sale tax considerations. Failing to report can trigger IRS notices and potential penalties.
Common traps and partial exclusions
The exclusion is not automatic. Owners who fall short of the two-out-of-five-year residency requirement, who used the exclusion on another property within the prior two years, or who acquired the home through a like-kind (1031) exchange may face reduced or eliminated exclusions. When part of the property was used for business or as a rental unit, the gain attributable to that portion may be fully taxable, and any depreciation previously claimed on that section is subject to recapture at a rate of up to 25%.
One mistake tax professionals see repeatedly: homeowners who fail to keep records of capital improvements. Without receipts or contractor invoices, sellers cannot increase their basis, which means more of the gain falls above the exclusion and into taxable territory. The IRS does not require a specific format for these records, but it does require that they exist.
What homeowners can do now
Sellers who suspect their gain may exceed the exclusion should start by reconstructing their cost basis as thoroughly as possible. That means gathering the original closing statement (HUD-1 or Closing Disclosure), receipts for capital improvements, and records of any depreciation claimed. A qualified tax professional can help identify which expenses count toward basis and which do not.
Timing matters, too. Married couples who can file jointly and meet the ownership and residency tests get the $500,000 exclusion, double the single-filer amount. For surviving spouses, selling within two years of a spouse’s death (and meeting other conditions) preserves access to the higher threshold. Divorced homeowners should review how the settlement allocated ownership and residency credit.
Beyond individual planning, some tax advisors suggest that homeowners in high-appreciation areas factor the potential capital gains hit into their retirement and relocation calculations, rather than treating the full sale price as spendable equity.
Will Congress raise the limits?
Senate Finance Committee hearing materials show that witnesses have urged Congress to raise or index the exclusion, arguing that the frozen caps no longer reflect typical gains in many markets and may discourage mobility among older homeowners who would otherwise sell and free up housing stock. Several proposals have surfaced in recent years, including during the 2024 presidential campaign cycle, but as of June 2026, no legislation adjusting the Section 121 thresholds has been enacted or advanced to a floor vote in either chamber.
The Treasury Department has summarized the existing rules in public guidance without signaling any administrative workaround, reinforcing that only Congress can change the statute. That leaves the exclusion frozen where it has been for nearly 30 years, while the housing market it was designed for continues to move further away from it.
For now, the burden falls on individual sellers to understand the rules, document their basis, and plan for a tax bill that previous generations of homeowners rarely had to think about.
