1033 Exchange Replacement Property: Similar Use, Deadline, and Basis

Under Section 1033 of the Internal Revenue Code, the rules for replacement property in a 1033 exchange come down to three things: the replacement has to be “similar or related in service or use” to what you lost, you have to buy it within a set window (usually two years, sometimes three or four), and you have to spend at least what you received to defer the whole gain.¹ Miss any of those and part or all of the gain becomes taxable in the year of the conversion. The wrinkle is that “similar or related in service or use” means different things depending on who you are and how the property was taken.

What Counts as Similar or Related in Service or Use

The IRS applies one of two tests, and which one you get depends on your relationship to the converted property.²

If You Used the Property Yourself: Functional Use

When you personally operated the property in your business, the replacement has to do the same job. A dry-cleaning plant lost to fire has to be replaced with another dry-cleaning operation. Swapping in a rental apartment building, or raw land held for future development, changes the functional use and blows the deferral.² Physical characteristics and day-to-day use both count.

If You Held It as an Investment: The Relationship Test

For property you leased out rather than used yourself, the IRS looks at your relationship to the asset instead of what the tenants did with it. What matters is the management effort you put in, the business risks you carried, and the type of income the property produced. An investor who loses a residential apartment building can replace it with a commercial office building and still qualify, because the role of landlord collecting rent is broadly the same.²

Either way, the replacement has to reflect the same kind of economic interest you lost. Replacing destroyed business inventory with a piece of equipment fails on both tests because the nature of the asset is completely different.

Buying Stock Instead of Property

You do not have to buy the replacement asset directly. Section 1033 also lets you acquire a controlling interest in a corporation that owns qualifying replacement property, meaning at least 80 percent of the total combined voting power of all voting stock and at least 80 percent of every other class of stock.¹ The corporation’s underlying property still has to meet the similar-or-related standard.

Condemned Real Estate Gets a Broader Standard

If your real property was taken by condemnation and you held it for business or investment, the strict “similar or related in service or use” rule is replaced by the broader “like-kind” test.³ Like-kind asks only whether both properties are real property held for business or investment. Specific use does not have to match. A condemned office building can be replaced with undeveloped investment land, or a condemned factory with a rental apartment building.

Two things to keep in mind. This broader test does not apply to property held primarily for sale, like a developer’s lot inventory. And it comes with a longer replacement window: three years after the close of the first tax year in which you realize any part of the gain, rather than the standard two.¹

Federally Declared Disasters Loosen the Rules Further

Business or Investment Property in a Disaster Area

If your business or investment property is destroyed in a federally declared disaster, any tangible property you acquire for use in any business qualifies as similar or related in service or use.² The replacement doesn’t even have to be in the disaster area. A restaurant owner whose building is destroyed in a hurricane could put the proceeds into a warehouse in another state and still defer.

Principal Residences

When your main home or its contents are destroyed in a federally declared disaster, insurance proceeds for unscheduled personal property (the everyday household items not itemized on your policy) are entirely tax-free, and you don’t have to replace them. The rest of the payout (for the home and any scheduled contents) is treated as a single conversion, so you can pool the proceeds and reinvest in a replacement home without tracking each item. The replacement window here stretches to four years after the close of the first tax year in which you realize the gain.¹

How Section 121 Interacts

If your principal residence is destroyed, the tax code treats it as a sale for purposes of the Section 121 home-sale exclusion. You can exclude up to $250,000 of gain, or $500,000 for married couples filing jointly, before Section 1033 even applies. When you then calculate the amount you need to reinvest under 1033, you reduce the amount realized by whatever gain Section 121 already excluded.⁴ For a lot of homeowners, Section 121 alone wipes out the gain and 1033 becomes unnecessary.

The Replacement Deadline

The clock starts when the property is converted, or on the earliest date you face a threat of condemnation, whichever comes first. It stops two years after the end of the first tax year in which you realize any part of the gain.¹ Receive proceeds and realize a gain in December 2025, and you have until December 31, 2027, to close on replacement property.

Three situations push the deadline further out:

Condemned business or investment real estate: three years.
Principal residence in a federally declared disaster: four years.¹
An IRS-granted extension, generally up to one additional year, for reasonable cause.

To request an extension, submit a written explanation of why you need more time, what steps you’ve taken to find replacement property, and details about the original conversion including adjusted basis, dates, and proceeds received. The IRS prefers requests filed before the replacement period ends but will consider late ones if you explain the delay. Construction that won’t finish in time counts as reasonable cause. High prices and thin inventory do not.⁵

Buying From a Related Party

The related-party restriction is narrower than it’s often described. It applies only to C corporations, partnerships in which C corporations own more than 50 percent of the capital or profits interest, and any other taxpayer whose total realized gain from involuntary conversions during the tax year exceeds $100,000.¹ If you fall into one of those categories, buying replacement property from a related party disqualifies deferral, unless that related party itself acquired the property from an unrelated person during the applicable replacement period. Individual taxpayers with realized gains of $100,000 or less are not affected by this rule at all.

How Much You Have to Spend, and What Your New Basis Becomes

Full deferral requires spending at least the amount you realized on the conversion. Spend less, and the shortfall is recognized as taxable gain right away.

Take a property with an adjusted basis of $150,000, converted for $400,000, producing a $250,000 realized gain. Buy replacement property for $500,000, and the entire $250,000 gain defers. Your basis in the new property is the $500,000 cost minus the $250,000 deferred gain, or $250,000.⁶

Buy a $350,000 replacement instead, and the $50,000 shortfall is taxable now. The remaining $200,000 rides along as deferred gain, so your basis in the replacement is $350,000 minus $200,000, or $150,000, which matches your original basis in the converted property.⁶ The deferred gain is baked into the basis, and it comes due whenever you eventually sell.

Making the Election on Your Return

Deferral is not automatic. You elect it by attaching a statement to your tax return for the year you realize the gain, describing what happened, when it happened, the proceeds received, and your intent to acquire qualifying replacement property.¹ The election is made even if you haven’t bought the replacement yet.

Casualty and theft losses are reported on Form 4684. Involuntary conversions of business property also flow through Form 4797, Sales of Business Property.⁷ If the replacement period later expires without a qualifying purchase, or you end up spending less than the amount realized, file an amended return (Form 1040-X for individuals) recognizing the previously deferred gain in the year of the original conversion. File as soon as you know the requirements won’t be met; waiting draws penalties and interest running from the original due date.

1
Office of the Law Revision Counsel. 26 USC 1033 – Involuntary Conversions
2
Internal Revenue Service. Publication 547 (2025), Casualties, Disasters, and Thefts
3
eCFR. 26 CFR 1.1033(g)-1 – Condemnation of Real Property Held for Productive Use in Trade or Business or for Investment
4
Office of the Law Revision Counsel. 26 USC 121 – Exclusion of Gain From Sale of Principal Residence
5
Internal Revenue Service. Involuntary Conversion: Get More Time to Replace Property
6
eCFR. 26 CFR 1.1033(b)-1 – Basis of Property Acquired as a Result of an Involuntary Conversion
7
Internal Revenue Service. About Form 4797, Sales of Business Property