Real Estate Tax Calc
The basic tax treatment of Section 1231 gains
Section 1231 of the Internal Revenue Code governs the tax treatment of gains and losses from the sale or exchange of property used in a trade or business and held for more than one year. For real estate investors, the most common Section 1231 assets are rental properties, commercial buildings, and other real estate used in business or held for investment.
The headline benefit of Section 1231 is this: if your Section 1231 gains for the year exceed your Section 1231 losses for the year, the net gain is treated as a long-term capital gain and taxed at the preferential long-term capital gains rates — 0%, 15%, or 20% depending on your taxable income, rather than at ordinary income rates that can reach 37%. If your Section 1231 losses exceed your gains, the net loss is treated as an ordinary loss, fully deductible against ordinary income with no $3,000 annual limitation. Section 1231 is thus the best of both worlds in theory: capital gain rates on the upside, ordinary loss treatment on the downside.
In practice, the treatment is complicated by two overrides: depreciation recapture under Sections 1245 and 1250 (which converts part of the gain back to ordinary income before Section 1231 applies) and the Section 1231 lookback rule (which can convert net 1231 gains into ordinary income if you had prior 1231 losses).
What qualifies as Section 1231 property
Section 1231 property includes real property used in a trade or business and held for more than one year, personal property used in a trade or business and held for more than one year (to the extent not recaptured under Section 1245), and certain timber, coal, iron ore, and livestock. For the typical real estate investor, the Section 1231 universe consists of:
Rental real estate (single-family homes, apartments, commercial buildings) held for more than one year. Land held for investment and used in a business. Leasehold improvements. Improvements to land used in business. The one-year holding period is measured from placed-in-service date to the date of sale — the same long-term capital gain threshold, but applied to business property specifically.
Personal residence sales are not Section 1231 transactions — they are governed by Section 121 (the home sale exclusion) and the capital gains rules for personal-use property. Section 1231 applies only when property has been used in a trade or business or held for investment.
Depreciation recapture comes first
Before Section 1231 applies to a real estate sale, depreciation recapture is computed and removed from the Section 1231 gain. This is the most important nuance in understanding the tax rate on a real estate sale.
Section 1245 recapture applies to personal property components (from a cost segregation study) and is taxed at ordinary income rates regardless of the Section 1231 rules. If you have Section 1245 assets, their gain up to the depreciation taken is ordinary income — removed from Section 1231 entirely.
Unrecaptured Section 1250 gain applies to the building itself and represents the straight-line depreciation claimed. It is taxed at a maximum rate of 25% — better than ordinary income but worse than the 15% or 20% long-term capital gains rate on the remainder. This portion is technically a Section 1231 gain, but it goes through the Unrecaptured Section 1250 Gain Worksheet in the Schedule D instructions, which applies the 25% rate specifically to that slice.
Only the gain above the depreciation claimed — the pure appreciation component — flows through Section 1231 unmodified and is eligible for the 0%, 15%, or 20% long-term capital gains rate. On a property held for many years with significant depreciation, this "clean" Section 1231 gain may be a smaller fraction of total gain than many investors expect.
The Section 1231 lookback rule: when gains become ordinary
The Section 1231 lookback rule prevents taxpayers from gaming the system by taking ordinary loss deductions in down years and then claiming preferential capital gain rates on later gains. The rule is straightforward: if you had net Section 1231 losses in any of the five preceding tax years that have not already been recaptured, your current-year net Section 1231 gain is treated as ordinary income to the extent of those prior unrecaptured losses.
Example: In 2021, you sold a rental property at a loss, generating a $40,000 net Section 1231 loss that you deducted as ordinary income. In 2026, you sell another property at a $75,000 net Section 1231 gain. The first $40,000 of that 2026 gain is treated as ordinary income (recaptured under the lookback rule), and the remaining $35,000 is a long-term capital gain at 0/15/20%.
The lookback period is rolling — each year you look back at the prior five years. Prior 1231 losses are recaptured in the order they were claimed, starting with the oldest within the five-year window. Once a prior year's 1231 loss has been fully recaptured by a later 1231 gain, it leaves the lookback history. The IRS requires you to track unrecaptured 1231 losses on a running schedule — many taxpayers miss this because the prior-year information is buried in old tax returns.
The actual tax rates on a 1231 gain
Breaking down a rental property sale's tax rate by component helps clarify where each dollar of gain is taxed:
Section 1245 recapture: taxed at your ordinary marginal rate (up to 37% federal).
Unrecaptured Section 1250 gain: taxed at a maximum of 25% federal. If your ordinary rate is below 25%, you pay that lower rate.
Section 1231 lookback recapture (prior unrecaptured 1231 losses): taxed at ordinary income rates.
Clean Section 1231 long-term capital gain (appreciation above all recapture): taxed at 0%, 15%, or 20% depending on taxable income.
The 3.8% Net Investment Income Tax (NIIT) applies on top of these rates for taxpayers whose MAGI exceeds $200,000 (single) or $250,000 (married filing jointly). State income tax stacks on top as well, with most states taxing gains at ordinary income rates.
The result is that a real estate sale typically produces gain taxed at multiple rates simultaneously: some at ordinary rates (Section 1245 recapture, possibly Section 1231 lookback), some at the 25% ceiling (unrecaptured 1250), and some at the 0/15/20% capital gains rate. Treating the entire gain as a flat 15% or 20% substantially underestimates the tax bill for any property with significant depreciation.
How to track prior-year Section 1231 losses
The IRS requires tracking Section 1231 gains and losses on a schedule that rolls forward year by year. The relevant worksheet is found in the Form 4797 instructions under 'Section 1231 Gains and Losses.' You must carry forward prior-year unrecaptured losses from each year's return to the next — it is not automatic; the tax software calculates it only if you enter the prior-year figures correctly.
To reconstruct prior-year Section 1231 loss carryforwards if you lack records: review Form 4797 from each return in the prior five tax years and look at the final total on Part I. Any year in which the net 1231 result was a loss, and that loss was deducted, contributes to the lookback pool unless already absorbed by a subsequent year's 1231 gain. The sum of unabsorbed prior-year losses is the lookback recapture amount that ordinary-incomes your current gain first.
If you are uncertain about your lookback balance, a tax professional can reconstruct it from prior returns. The stakes are real: incorrectly ignoring the lookback rule understates ordinary income and overstates capital gain income — two different tax rates, potentially 20+ percentage points apart.
Planning around Section 1231 gains
Understanding the rate components opens planning opportunities. If you have prior Section 1231 losses that will ordinary-income your 2026 gain under the lookback rule, accelerating other ordinary deductions (bonus depreciation, retirement plan contributions, charitable deductions) can offset the recaptured ordinary income.
Conversely, if you have prior-year capital losses carried forward, they can offset the clean Section 1231 long-term capital gain portion but generally cannot offset Section 1245 ordinary recapture or Section 1231 lookback ordinary income. Knowing which losses can offset which types of income is essential for accurate tax planning before you close.
A 1031 like-kind exchange defers all four components — 1245 recapture, unrecaptured 1250 gain, 1231 lookback recapture, and clean capital gain — into the replacement property. The exchange does not change the character of the deferred gain; it simply postpones recognition. When the replacement property is eventually sold without another exchange, all the deferred character pieces resurface. This is why a chain of 1031 exchanges can accumulate significant embedded ordinary income in the form of prior Section 1245 recapture from each leg.
How to report Section 1231 gains on Form 4797
The sale of a business-use real property is reported on Form 4797, Sales of Business Property. Part I covers 1231 gains and losses held more than one year. Part II covers ordinary gains and losses. Part III figures the Section 1245 and 1250 recapture.
The computation flows: Part III first separates the ordinary income component (Section 1245 recapture) and a portion of Section 1250 recapture if applicable. The remainder flows to Part I as Section 1231 gain. If total 1231 gains in Part I exceed 1231 losses, the net gain carries to Schedule D as long-term capital gain (where it goes through the Unrecaptured Section 1250 Gain Worksheet for the 25%-capped slice and the capital gains rate worksheet for the rest). If losses exceed gains, the net loss flows to Schedule 1, line 4, as an ordinary deduction against income.
Tax software handles this routing automatically if you enter each asset sold in the asset sale module with the correct property type and prior depreciation data. The single most important input is your cumulative depreciation claimed — errors in this figure drive errors in all three buckets of recapture and gain.
Frequently asked questions
What is the tax rate on Section 1231 gain?
Net Section 1231 gains are taxed at long-term capital gains rates (0%, 15%, or 20%), but two overrides apply first: depreciation recapture is taxed at higher rates (up to 25% for unrecaptured Section 1250 gain and at ordinary rates for Section 1245 recapture), and prior-year Section 1231 losses may convert current gains to ordinary income under the lookback rule.
What is the Section 1231 lookback rule?
If you had net Section 1231 losses in any of the previous five years that haven't been recaptured, those losses convert your current Section 1231 gains to ordinary income to the extent of the prior losses.
Can Section 1231 losses offset ordinary income?
Yes. Net Section 1231 losses are treated as ordinary losses, fully deductible against ordinary income with no annual limitation — unlike capital losses, which are limited to $3,000 per year.
How does a 1031 exchange affect Section 1231 gain?
A 1031 exchange defers recognition of Section 1231 gain (including all recapture components) into the replacement property. The gain's character — ordinary recapture, 25%-capped 1250 gain, and clean capital gain — is preserved in the replacement property's basis and resurfaces when that property is eventually sold without a further exchange.
Are Section 1231 gains subject to the 3.8% Net Investment Income Tax?
Yes. The NIIT applies to net investment income, which includes net capital gain from the disposition of property held in a trade or business if that trade or business is a passive activity. Most rental real estate investors are passive participants and owe NIIT on gains above the MAGI thresholds.
How do I track prior Section 1231 losses?
Use the Section 1231 Gains and Losses worksheet in the Form 4797 instructions, rolling forward each prior year's net 1231 loss that was deducted as ordinary income. Unabsorbed losses from each year remain in the lookback pool for five years.
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.