IRS Short Sales: Section 1233, Wash Sales, and Reporting

A short sale is taxed when you close the position, not when you open it, and the gain or loss is almost always a short-term capital gain taxed at your ordinary income rate. The short sale tax rules in IRC Section 1233 add a second layer: if you also own stock that is substantially identical to what you sold short, those rules can force short-term treatment on a gain, force long-term treatment on a loss, and reset the holding period on the stock you already own. Add the wash sale rule, the constructive sale rule, borrow fees, payments in lieu of dividends, and the 3.8% net investment income tax, and a profitable short trade can carry more moving parts than most investors expect.

When the Tax Hits and How Gain or Loss Is Calculated

Opening a short position is not a taxable event. You borrow shares from your broker, sell them, and the proceeds sit as collateral. Nothing is recognized for tax purposes until you close (or “cover”) the position by delivering replacement shares to the lender.¹

Your gain or loss is the net proceeds from the initial sale minus the cost of the covering property, including commissions on both sides. Sell short at $100 and cover at $70, and you have a $30 per-share gain. Cover at $120 instead, and you have a $20 per-share loss.

The tax year is the year you cover. If you sold short in December 2025 and buy to cover in January 2026, the whole transaction lands on your 2026 return.¹ This trips up traders who assume the cash they received in December is taxable in December.

If you use shares you already own to close the short instead of buying replacements, your gain or loss is measured against your original adjusted basis in those specific shares, not their market value on the delivery day.

Why Most Short Sale Gains Are Short-Term

Character depends on the holding period of the covering property. In a normal buy-to-cover, you purchase shares and deliver them the same day, so the holding period is effectively zero. That makes almost every short sale gain a short-term capital gain, taxed at ordinary income rates.²

Section 1233 Traps When You Also Own the Stock

The rules get harder when you hold, or acquire, stock that is substantially identical to what you shorted. Congress wrote IRC Section 1233 to block two games: turning a short-term gain into a long-term gain, and turning a long-term loss into a more useful short-term loss.³

If You’ve Held the Identical Stock a Year or Less

If, on the date you open the short, you have held substantially identical property for one year or less, or if you acquire substantially identical property after opening the short but before closing it, two things happen. Any gain on closing the short is automatically short-term regardless of how long you actually held the covering shares. And the holding period on that substantially identical property resets to zero on the day the short closes.³

The reset is what stings. Hold 500 shares for 11 months, open a short against the same ticker, and when you close the short, the clock on those 500 shares starts over. Months of progress toward long-term treatment on a separate position vanish.

If You’ve Held the Identical Stock More Than a Year

If you’ve held substantially identical property for more than one year on the date of the short sale, any loss on closing the short is automatically long-term, even if the covering shares were held for days.³ Long-term losses are less useful because they offset long-term gains first, which are already taxed at preferential rates.

What Counts as Substantially Identical

Substantially identical property covers the same stock and also options, warrants, and convertible securities tied directly to the shorted stock. Publication 550 treats this as a facts-and-circumstances question, but the practical test is whether the two instruments carry the same investment risk and are effectively interchangeable.⁴

Payments in Lieu of Dividends

The original lender still expects any dividends the company pays while their shares are on loan, so you owe a payment in lieu (PIL) equal to the dividend. Treatment depends on how long the short stays open.

Close the short on or before the 45th day after opening it, and no deduction is allowed for the PIL. The payment gets capitalized into the basis of the stock used to close the position, which reduces your gain or increases your loss on the trade. For extraordinary dividends, this capitalization rule stretches to positions closed within one year of the short.⁵

Hold the short longer than 45 days and the PIL is generally deductible as investment interest expense under IRC Section 163(d)(3)(C).⁶ That means the deduction is capped at your net investment income for the year, with any excess carried forward. You compute the limit on Form 4952 and report the deductible amount on Schedule A.⁷ Payments in lieu of interest on borrowed bonds get investment interest expense treatment regardless of holding period, subject to the same limit.

Borrow Fees and Margin Interest

Brokers charge stock borrowing fees, sometimes called hard-to-borrow fees or loan premiums. For most individual investors, these qualify as deductions “in connection with personal property used in a short sale” under IRC Section 67(b)(8), which excludes them from the category of miscellaneous itemized deductions. That distinction matters because miscellaneous itemized deductions are currently suspended, while Section 67(b)(8) deductions survive.

Margin interest on loans used to buy covering property is investment interest expense under IRC Section 163, subject to the same net investment income cap that applies to PILs.⁶

Short Sales Against the Box and Constructive Sales

Shorting a stock you already own used to be a way to lock in a gain without triggering tax, by keeping both the long and short positions open. IRC Section 1259 ended that by treating the setup as a “constructive sale” of the appreciated stock.⁸

The rule fires when the transaction effectively eliminates both your risk of loss and your opportunity for further gain. When it applies, you recognize gain as though you sold the underlying stock at fair market value on the date you opened the short, with character based on how long you held the underlying stock.

There is one narrow safe harbor. You avoid constructive sale treatment only if all three conditions hold: you close the short on or before the 30th day after the end of the tax year, you keep the underlying stock fully unhedged for at least 60 days starting from the day the short closes, and your risk of loss is not reduced during that 60-day window.⁸ Miss any one and the constructive sale stands. If you recognized the constructive sale gain, your basis in the underlying stock is increased by that amount so the eventual close of the short does not tax the same gain twice.

Wash Sales Apply to Shorts

Under IRC Section 1091(e), closing a short sale at a loss and entering a new short of substantially identical stock within 30 days before or after the closing date disallows the loss. Buying substantially identical stock inside that 61-day window has the same effect.⁹

The disallowed loss is added to the basis of the replacement position, so it comes back when that position closes. The problem is timing: if the replacement doesn’t close until the next tax year, the loss you were counting on disappears from the current return. Active short sellers who cycle the same ticker are the most likely to trip this without noticing.⁴

Straddles and Section 1256 Contracts

If the short is part of a straddle, meaning you hold offsetting positions in the same or related property, IRC Section 1092 defers your loss on one leg to the extent of unrealized gain on the offsetting leg.¹⁰ The deferred loss carries forward and becomes deductible later, subject to the same limitation.

Shorts of Section 1256 contracts, such as regulated futures, live in a separate regime. They are marked to market at year-end, and gain or loss is split 60% long-term and 40% short-term regardless of holding period.¹¹ The blended rate is generally more favorable than pure short-term treatment.

The 3.8% Net Investment Income Tax

Short sale gains count as net investment income for the 3.8% Net Investment Income Tax. The surtax applies to the lesser of your net investment income or the amount by which your modified adjusted gross income exceeds $200,000 (single), $250,000 (married filing jointly), or $125,000 (married filing separately).¹² Those thresholds are not indexed for inflation.¹³

For a high-income short seller, a short-term gain can carry a combined 40.8% federal rate: 37% ordinary plus 3.8% NIIT. Easy to overlook when sizing the trade.

When Your Broker Lends Out Your Shares

If your broker lends your shares to facilitate someone else’s short and a dividend is paid while your shares are on loan, you receive a “substitute payment” instead of an actual dividend. Substitute payments do not qualify for the 0%, 15%, or 20% qualified dividend rates. They are ordinary income at your marginal rate.⁴

Your broker reports the amount on Form 1099-MISC, Box 8, rather than on Form 1099-DIV.¹⁴ You report the amount as other income on Schedule 1 (Form 1040), line 8z.⁴ Standard margin agreements typically give brokers blanket permission to lend, so you may not know it happened until the 1099-MISC arrives. If you want to prevent it, check whether your broker offers a way to opt out.

Reporting on Form 8949 and Schedule D

Brokers report short sale proceeds on Form 1099-B, usually in the year of the initial sale. You calculate and report your gain or loss on Form 8949.¹⁵

The date columns confuse people. For a short sale, column (b), “Date Acquired,” is the date you acquired the property used to close the short, and column (c), “Date Sold or Disposed Of,” is the date you delivered that property to close the position.¹⁶ In a standard buy-to-cover, they are typically the same trade date.

Enter the transaction in Part I for short-term or Part II for long-term based on the final character after applying Section 1233. If the 1099-B suggests a different holding period than what the anti-abuse rules require, use the correct Part and the appropriate adjustment code to explain the difference. Code W applies to a wash-sale disallowed loss.¹⁷

If you capitalized a PIL under the 45-day rule, add that amount to the basis on Form 8949. Your broker will generally report total payments in lieu on Form 1099-MISC, and you handle the capitalization reconciliation yourself.

The totals flow to Schedule D, which nets short-term against long-term. If total capital losses exceed total capital gains, you can deduct up to $3,000 of the excess against other income ($1,500 if married filing separately), with the rest carried forward.¹⁸

Constructive sale gain under Section 1259 is also reported on Form 8949 and Schedule D, with the sale date being the day you opened the short against the box. Track those carefully so the same gain doesn’t get reported twice when the short later closes.

Penalties for Getting It Wrong

The IRS imposes a 20% accuracy-related penalty on any underpayment from negligence or substantial understatement of income tax.¹⁹ For individuals, an understatement is “substantial” when it exceeds the greater of $5,000 or 10% of the tax that should have been shown on the return. Given how tangled the Section 1233 holding period rules and the Section 1259 constructive sale rules can be, short sale errors above that threshold happen more often than they should.

You can avoid the penalty by showing reasonable cause and good faith. Keep records of every purchase, sale, cover date, and payment in lieu, and note which Section 1233 rules you applied and why. That documentation is the best defense if the return is questioned.

1
eCFR. 26 CFR 1.1233-1 – Gains and Losses From Short Sales
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Internal Revenue Service. Topic No. 409 – Capital Gains and Losses
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Office of the Law Revision Counsel. 26 USC 1233 – Gains and Losses From Short Sales
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Internal Revenue Service. Publication 550 – Investment Income and Expenses
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Office of the Law Revision Counsel. 26 USC 263 – Capital Expenditures
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Office of the Law Revision Counsel. 26 USC 163 – Interest
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Internal Revenue Service. About Form 4952, Investment Interest Expense Deduction
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Office of the Law Revision Counsel. 26 USC 1259 – Constructive Sales Treatment for Appreciated Financial Positions
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Office of the Law Revision Counsel. 26 USC 1091 – Loss From Wash Sales of Stock or Securities
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Office of the Law Revision Counsel. 26 USC 1092 – Straddles
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Office of the Law Revision Counsel. 26 USC 1256 – Section 1256 Contracts Marked to Market
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Internal Revenue Service. Net Investment Income Tax
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Internal Revenue Service. Questions and Answers on the Net Investment Income Tax
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Internal Revenue Service. Instructions for Forms 1099-MISC and 1099-NEC
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Internal Revenue Service. About Form 8949, Sales and Other Dispositions of Capital Assets
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Internal Revenue Service. 2025 Instructions for Form 8949
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Internal Revenue Service. Instructions for Form 8949
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Office of the Law Revision Counsel. 26 USC 1211 – Limitation on Capital Losses
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Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments