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How Does the Net Section 1256 Loss Carryback Work?

A net Section 1256 loss can be carried back three years, earliest first, against earlier Section 1256 gains only. How much, which years, box D, Form 1045 or 1040-X.

By Owen Monagan8 min read
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For people filing under Section 1256, a net Section 1256 loss can be carried back to the three tax years before it, earliest first. In each year it offsets only that year's Section 1256 gain. The election is box D on Form 6781, and the claim is Form 1045 or Form 1040-X. As of October 2026 the IRS has issued no guidance on whether event contracts are Section 1256 contracts.

Can you carry back a Section 1256 loss? Three years, against Section 1256 gains only

Yes, for an individual who makes the election. Under IRC §1212(c), a net Section 1256 contracts loss can go back to each of the three tax years before the loss year. Corporations, estates and trusts cannot make the election.

There is one hard limit. In each earlier year, the loss can only offset that year's net Section 1256 gain. A year with no Section 1256 gain absorbs nothing.

The calendar sets which years a loss can reach:

Loss yearGoes first toThenThen
2025202220232024
2026202320242025

Regulated futures contracts and nonequity options are Section 1256 contracts by statute. Event contracts are not named in it. Of the people we've seen file event contracts, Section 1256 is one of the three most common ways. For people who file them under Section 1256 because of the 60/40 split, the carryback is part of what that involves. Everything below applies to them.

Which years does a Section 1256 loss carry back to? Earliest first, one year at a time

The whole loss goes to the earliest of the three years first. What that year cannot absorb moves to the next year, then the next.

The worked years: a $30,000 loss reaching 2023, 2024 and 2025

Take a single filer with a $30,000 net Section 1256 loss in 2026. Each earlier year's Section 1256 result went on Form 6781 that year. There are no other capital gains or losses in any year. These numbers are illustrative.

YearNet Section 1256 resultCarryback it absorbsStill to place
2026 (loss year)$30,000 loss$27,000
2023$0$0$27,000
2024$8,000 gain$8,000$19,000
2025$12,000 gain$12,000$7,000

Only $27,000 of the $30,000 can travel. The other $3,000 stays in 2026, as the next section explains. 2023 had no Section 1256 gain, so it takes nothing. 2024 and 2025 take $20,000 between them. The last $7,000 carries forward to 2027.

How the loss lands in each year: 40% short-term, 60% long-term

The carried-back loss keeps the 60/40 split. Of the $8,000 that reaches 2024, $3,200 counts as a short-term Section 1256 loss and $4,800 as long-term. The $12,000 in 2025 splits into $4,800 and $7,200.

What that is worth depends on each earlier year's whole return: its brackets, the 60/40 rates and any tax tied to income. So this guide shows what moves between years, not a refund figure.

How much of a Section 1256 loss can be carried back? The smaller-of rule

Form 6781 sets the amount as the smaller of two figures. One is how far your Section 1256 losses exceed your Section 1256 gains plus $3,000. The other is the capital loss carryover you would have without the carryback. Each earlier year then has its own cap.

The $3,000 stays in the loss year

The $3,000, or $1,500 if married filing separately, is the part of a capital loss that can come off ordinary income each year under §1211(b). The form keeps it in the loss year rather than sending it back. That is why a $30,000 loss sends at most $27,000 back.

Other capital gains in the loss year shrink the second figure. A $10,000 stock gain in 2026 would absorb $10,000 of the loss first, leaving less to carry back.

Each earlier year's cap: the lesser of two gains

An earlier year can absorb no more than its net Section 1256 contract gain. The statute defines that as the lesser of two numbers:

  • The Section 1256 gain alone: that year's capital gain counting only Section 1256 contracts.
  • The whole capital gain: that year's capital gain counting everything.

Both are figured before any carryback arrives. So a 2024 with an $8,000 Section 1256 gain and a $5,000 stock loss has $3,000 of capital gain overall. That year absorbs $3,000, not $8,000.

One more limit applies. A carryback cannot create or increase a net operating loss in the earlier year.

Do your earlier years have Section 1256 gains to absorb it? The event-contract question

The carryback reads each earlier year's Section 1256 gain. For an event-contract trader, that depends on how those winning years were reported.

Winning years filed on Form 6781

If the earlier winning years went on Form 6781, those returns show a Section 1256 gain. That is the case in the worked years above. The carryback has something to absorb it, up to each year's cap.

Winning years filed on Form 8949 or as gambling

If the winning years went on Form 8949 as ordinary capital gains, or on Schedule 1 as gambling winnings, the returns as filed show no Section 1256 gain. Form 6781 measures the earlier year by the gain "reported on line 16 of Schedule D" and by what you "would report" counting only Section 1256 contracts.

Whether a carryback can reach those years without first refiling them under Section 1256 is not addressed by any IRS guidance. It is an open question, not a settled step.

The calendar matters too. Kalshi has been a designated contract market since November 2020, so its earlier years can hold event-contract activity. Polymarket US was designated in July 2025, so a 2026 loss reaches its activity in 2025 only.

How do you elect the Section 1256 loss carryback? Box D and line 6

The election is made on the loss year's Form 6781. It takes two entries there, and one on each earlier year's amended form.

The loss year: box D and line 6

The election is box D, the net Section 1256 contracts loss election. The amount carried back goes on line 6 as a positive number. In the worked years that is $20,000. Line 7 becomes a $10,000 loss, and lines 8 and 9 split it $4,000 short-term and $6,000 long-term. If box D is not checked, line 6 is -0-.

No IRS form or instruction says how a late election is made for a loss year filed without box D, so that question is unsettled.

The earlier year: line 1 of an amended Form 6781

Each year the loss reaches gets an amended Form 6781. The carryback goes on line 1, labeled "Net section 1256 contracts loss carried back from" and the loss year, with the amount as a loss. The line-by-line walk-through is in the Form 6781 guide for event contracts.

Form 1045 or Form 1040-X: how is the carryback claimed, and by when?

There are two ways to claim it, each with its own deadline. Form 1045 asks the IRS to act within 90 days and closes one year after the loss year. Form 1040-X is processed as a claim and stays open three years.

The deadlines by loss year

Loss yearForm 1045 windowForm 1040-X window
2025After the 2025 return is filed, to December 31, 2026To April 2029, or later if extended
2026After the 2026 return is filed, to December 31, 2027To April 2030, or later if extended

The Form 1045 window is one year after the end of the loss year. The Form 1040-X window is three years after the loss-year return's due date, including extensions. Both dates come from the IRS instructions, worked out for these two years.

Form 1045: one application, 90 days

Form 1045 is an application for a tentative refund. One application covers every earlier year, in one pair of before-and-after columns per year. It cannot be filed before the loss-year return. The IRS acts within 90 days, and paying the refund does not mean it has accepted the figures. The form, line by line, is on the Form 1045 page.

Form 1040-X: one return per year

Form 1040-X takes one return for each year the loss reaches, with "Carryback Claim" written at the top. Each one attaches the amended Form 6781 and Schedule D for that year. How amending works for prediction market losses is in how to amend a tax return for prediction market losses.

What happens to the part that is not carried back?

It carries forward under the normal capital loss rules. In the worked years, $7,000 goes to 2027. It offsets capital gains first, then up to $3,000 a year of other income. It still counts as a Section 1256 loss in those later years.

A carryback also changes the earlier year's adjusted gross income. Deductions and credits tied to income get refigured, and the alternative minimum tax can change. Form 1045 has lines for each.

The three ways a losing year can be used, including the forward-only path, are compared in are prediction market losses tax deductible.

How Realize handles the carryback

Realize reads your Kalshi and Polymarket US trades read-only and builds the loss year's Form 6781. It also shows each year's net Section 1256 result for the venues you connect, which is the figure the carryback reads.

Realize does not check box D for you or put a dollar figure on the carryback. It does not produce Form 1045, the amended earlier-year forms or a Form 1040-X. Realize also offers a call with a CPA. For the wider picture, start at the Prediction Market Tax Center.

Sources

Questions people ask

Can you carry back Kalshi or Polymarket losses?

Only if you file them under Section 1256, and only against Section 1256 gains in the three years before. The section on earlier gains covers which years count.

What if I had no Section 1256 gains in the last three years?

Then the carryback absorbs nothing. The loss carries forward instead, at up to $3,000 a year against other income after it offsets capital gains.

Does a carried-back loss offset ordinary income in the earlier year?

No. It offsets only that year's net Section 1256 gain, and never more than that year's total capital gain.

Do I need Form 1045 to carry back a Section 1256 loss?

No. Form 1045 is one way to claim it. Form 1040-X is the other, one return per year, on a longer deadline.

Can part of the loss go back and the rest go forward?

Yes. Whatever the earlier years do not absorb carries forward. It still counts as a Section 1256 loss in later years.

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