Section 1231 Five-Year Lookback Calculator
Enter the current Section 1231 result and the unused loss balances from the last five years. The calculator applies the lookback rule oldest first and shows the ordinary-income amount, capital-gain amount, expiring loss, and balance entering next year.
Gain treated as ordinary income$30,000.00
- Current net Section 1231 result
- $50,000.00
- Prior nonrecaptured Section 1231 losses
- $30,000.00
- Gain treated as long-term capital gain
- $20,000.00
- Current ordinary Section 1231 loss
- $0.00
- Unused loss expiring after this year
- $0.00
- Nonrecaptured loss balance entering next year
- $0.00
- Estimated federal tax on current net gain
- $12,600.00
- Estimated tax added by the lookback rule
- $5,100.00
Oldest-first loss allocation
| Loss year | Beginning unused loss | Applied to current gain | Remaining | Treatment |
|---|---|---|---|---|
| 2,021 | $12,000.00 | $12,000.00 | $0.00 | Remaining balance expires after this year |
| 2,022 | $0.00 | $0.00 | $0.00 | Remaining balance carries forward |
| 2,023 | $18,000.00 | $18,000.00 | $0.00 | Remaining balance carries forward |
| 2,024 | $0.00 | $0.00 | $0.00 | Remaining balance carries forward |
| 2,025 | $0.00 | $0.00 | $0.00 | Remaining balance carries forward |
Prior-year fields should contain remaining nonrecaptured Section 1231 loss balances, not original loss amounts.
Depreciation recapture under Sections 1245, 1250, 291, and similar rules should be calculated before entering current Section 1231 gains.
How to use this calculator
- Enter the current tax year so the five prior-year buckets are labeled correctly.
- Enter current-year Section 1231 gains and losses after separate depreciation-recapture calculations.
- Enter only the remaining nonrecaptured loss balance for each of the five prior years.
- Review the allocation table to see which loss years are used, expire, or carry forward.
- Use the ordinary and capital-gain tax rates only as a rough federal tax estimate.
How the Section 1231 lookback is calculated
Section 1231 generally lets net gains from qualifying business property receive long-term capital gain treatment while net losses are ordinary losses. Section 1231(c) adds a lookback rule: if you have a current net Section 1231 gain, prior nonrecaptured net Section 1231 losses from the preceding five years can cause part of that gain to be treated as ordinary income.
The calculator first nets the current year:
N = current Section 1231 gains - current Section 1231 losses
It then adds the five remaining prior-year loss balances:
P = B5 + B4 + B3 + B2 + B1
If N is positive, the ordinary-income portion is O = min(N, P). The remaining long-term capital gain is C = N - O. If N is zero or negative, there is no current lookback recapture; the current ordinary Section 1231 loss is -N when losses exceed gains.
How the loss buckets move
The allocation table applies the ordinary-income amount to prior losses in chronological order: five years ago first, then four, three, two, and one year ago. For each bucket, the applied amount is the smaller of the unused balance and the ordinary-income amount still unallocated. The remaining five-years-ago balance expires after the current year. Remaining balances from the other four prior years carry into next year, along with any new current-year net Section 1231 loss.
This oldest-first schedule matters because a taxpayer can have enough current gain to use an older loss before it expires while still leaving newer loss buckets available for later years. It also makes Form 4797 line 8 easier to trace because the total prior nonrecaptured losses and the amount recharacterized as ordinary income are shown separately.
What moves the result most
The ordinary-income amount is driven by two numbers: the positive current net Section 1231 gain and the total remaining prior nonrecaptured losses. The estimated tax effect depends on the spread between the ordinary income rate and the long-term capital gain rate. If those rates are equal, the calculator may still show ordinary-income recharacterization, but the estimated lookback tax premium is zero.
What this calculator leaves out
This tool does not decide whether an asset or sale qualifies for Section 1231 treatment. It also does not compute Section 1245, Section 1250, Section 291, casualty and theft netting, installment sale treatment, like-kind exchange effects, partnership or S corporation basis limits, AMT, the net investment income tax, state tax, or taxable-income stacking. The prior-year inputs must already be reduced for amounts used in intervening years.
Worked example
Suppose the current tax year is 2026. Current Section 1231 gains are $50,000 and current Section 1231 losses are $0, so the current net Section 1231 gain is $50,000. The taxpayer has $12,000 of unused loss from 2021 and $18,000 from 2023, for total prior nonrecaptured losses of $30,000.
The lookback rule treats $30,000 of the current gain as ordinary income, leaving $20,000 as long-term capital gain. The allocation uses all $12,000 from 2021 first and all $18,000 from 2023 next. With a 32% ordinary rate and a 15% capital-gain rate, estimated federal tax on the gain is $12,600, and the estimated added tax from lookback recharacterization is $5,100.
Common questions
What is the Section 1231 five-year lookback rule?
The rule recharacterizes current net Section 1231 gain as ordinary income to the extent of nonrecaptured net Section 1231 losses from the preceding five tax years. Only a positive current net Section 1231 gain can be recharacterized. Any gain left after that lookback amount remains long-term capital gain.
Where do I find prior nonrecaptured Section 1231 losses?
Start with filed returns, Form 4797 records, and any workpapers that tracked Section 1231 losses and later gains. Each prior-year field should contain the remaining unused balance, not the original loss before later years used part of it.
Why are prior losses applied beginning with the earliest year?
The five-year lookback period ages out, so the oldest loss is the one most at risk of expiring after the current year. Applying gain chronologically shows which older balances are absorbed before newer balances carry forward.
Does a current net Section 1231 loss become an ordinary loss?
In the simplified netting modeled here, a current net Section 1231 loss is shown as an ordinary Section 1231 loss. The calculator also adds that loss to the balance entering next year because it can become part of the five-year lookback history.
Is Section 1245 or Section 1250 depreciation recapture included?
No. Depreciation recapture and related special rules should be calculated before entering the current Section 1231 gains. Enter the Section 1231 amount that remains after those separate recapture calculations.
What happens to an unused loss after five years?
The oldest bucket is available for the current calculation. Any amount left in that five-years-ago bucket after applying the current net gain is shown as expiring after this year and is not included in the next-year balance.