Stock swap taxation turns on one question: does your exchange qualify for deferral under the federal corporate reorganization rules? If it does, you postpone the tax until you sell the new shares. If it doesn’t, the IRS treats the swap as a sale of your old stock at fair market value followed by a purchase of the new stock, and the full gain is taxable in the year of the exchange.1eCFR. 26 CFR 1.1001-1 – Computation of Gain or Loss
The Default Rule Is That Swaps Are Taxable
Any time you exchange property for materially different property, the IRS treats that as a taxable event.1eCFR. 26 CFR 1.1001-1 – Computation of Gain or Loss Swapping shares of Company A for shares of Company B counts. Your gain or loss equals the fair market value of what you received minus your adjusted basis in the old stock.2Office of the Law Revision Counsel. 26 U.S. Code 1001 – Determination of Amount of and Recognition of Gain or Loss
Every stock swap is presumed taxable unless a specific code provision says otherwise, and the shareholder carries the burden of qualifying for deferral. If the deal doesn’t fit one of the defined exceptions, the full gain is recognized immediately even though no cash changed hands.
One boundary worth setting: the like-kind exchange rules under Section 1031 do not apply to stocks, bonds, or other securities. That deferral mechanism covers real property only. For stock, deferral comes from the reorganization and controlled-corporation rules described below.
How a Taxable Swap Is Calculated
When the swap doesn’t qualify for deferral, the math looks like an ordinary sale. Subtract your adjusted basis in the old shares from the fair market value of the new shares (plus any cash or other property received). A positive number is your gain.
The character depends on how long you held the original stock. One year or less produces short-term capital gain, taxed at ordinary income rates. More than one year produces long-term capital gain at preferential rates.3Internal Revenue Service. Topic No. 409, Capital Gains and Losses For 2026, the long-term rates are 0%, 15%, or 20% depending on taxable income and filing status, with most taxpayers falling in the 15% bracket.
Your basis in the new stock is its fair market value on the exchange date, and your holding period on the new stock starts fresh. You paid tax on the full gain, so the slate is clean going forward.
When a Swap Qualifies for Deferral
The main escape from immediate tax is a qualifying corporate reorganization. Section 368 defines the reorganization types, including statutory mergers, stock-for-stock acquisitions, recapitalizations, and changes in identity or form.4Office of the Law Revision Counsel. 26 U.S. Code 368 – Definitions Relating to Corporate Reorganizations The non-recognition rule for shareholders lives in Section 354: no gain or loss is recognized when you exchange stock in a corporation that’s party to a reorganization solely for stock in that corporation or another corporation involved in the reorganization.5Office of the Law Revision Counsel. 26 USC 354 – Exchanges of Stock and Securities in Certain Reorganizations The word “solely” carries weight. If all you receive is stock in the acquiring company, the entire gain is deferred.
The acquiring corporation’s advisors structure the deal to qualify, and as a shareholder you typically receive a letter or prospectus stating whether the exchange is intended to be tax-free. The IRS isn’t bound by that characterization, but for most public-company mergers the treatment stated in the deal documents is what applies.
A separate deferral rule under Section 351 covers a different situation: transferring property, including stock in another company, to a corporation in exchange for that corporation’s stock when you or your group controls the corporation immediately after the exchange.6Office of the Law Revision Counsel. 26 U.S. Code 351 – Transfer to Corporation Controlled by Transferor Control means at least 80% of total combined voting power and 80% of every other class of stock.4Office of the Law Revision Counsel. 26 U.S. Code 368 – Definitions Relating to Corporate Reorganizations This comes up when forming a new corporation or moving investments into a holding company.
Cash or Other Property in the Deal Triggers Partial Tax
Most reorganizations are not purely stock-for-stock. The acquirer may pay part of the price in cash, assume debt, or add warrants. Anything you receive beyond qualifying stock is called “boot,” and it triggers gain recognition.7Office of the Law Revision Counsel. 26 USC 356 – Receipt of Additional Consideration
The taxable amount is the lesser of the boot received or your total realized gain. That cap matters. Say your old stock had a basis of $15,000 and the total package you received was worth $22,000, giving you a $7,000 realized gain. If $3,000 came as cash, you recognize $3,000. If the boot had been $10,000, you would still only recognize $7,000, because the recognized gain can never exceed the gain that actually exists.
Recognized boot gain is generally capital gain, assuming you held the original stock as a capital asset. Whether it’s short-term or long-term depends on your holding period in the old shares. The rest of the gain stays deferred, embedded in the basis of your new stock.
Losses Don’t Come Out in a Deferred Swap
This one surprises people. If your old stock was worth less than your basis, you cannot recognize that loss in a reorganization exchange even if you also received boot. Section 356(c) is explicit on the point.7Office of the Law Revision Counsel. 26 USC 356 – Receipt of Additional Consideration
The loss isn’t erased. It’s preserved in your basis in the new stock, which will be higher than the current market value of those shares. When you eventually sell, that built-in loss will reduce your gain or produce a deductible loss then. But if you were counting on booking a loss in the year of the merger, the reorganization rules block it.
Basis and Holding Period in the New Stock
Getting the basis right is where the long-term money sits. A mistake here follows you until you sell.
For a fully taxable swap, the basis of your new stock is its fair market value on the exchange date, and the holding period starts fresh.
For a deferred swap, Section 358 carries the old basis over with adjustments: take the old stock’s basis, subtract any cash or other property received, and add any gain recognized.8Office of the Law Revision Counsel. 26 USC 358 – Basis to Distributees A worked example: your old stock had a $10,000 basis, you received new stock plus $2,000 cash, and your total realized gain was $5,000. You recognize $2,000 (the boot). Your new basis is $10,000 minus $2,000 plus $2,000, which is $10,000. The remaining $3,000 of deferred gain is baked into that basis and appears when you sell. If you receive only stock and no boot, the new stock’s basis simply equals the old stock’s basis, dollar for dollar.
Your holding period carries over in a deferred swap. Under Section 1223, the time you held the old stock tacks onto the new stock, provided the new stock’s basis is derived from the old stock’s basis and the old stock was a capital asset.9Office of the Law Revision Counsel. 26 U.S. Code 1223 – Holding Period of Property Held the originals three years before the merger? The new shares qualify for long-term treatment on day one.
Cash Paid for Fractional Shares
When the exchange ratio in a merger doesn’t divide evenly into your holdings, you may be entitled to a fractional share. Most companies pay cash for the fraction rather than issue it. That cash is taxable as capital gain, calculated as if you received the fractional share and immediately sold it. Your gain equals the cash received minus the portion of your basis allocable to the fraction.
The amounts are usually small, but they still need to be reported. Even when the deal documents describe the transaction as fully tax-deferred, the cash-in-lieu payment is the piece that isn’t.
The 3.8% Surtax for Higher Earners
Capital gains from a stock swap, whether recognized immediately or realized later after deferral, can also trigger the Net Investment Income Tax. This 3.8% surtax applies to the lesser of your net investment income or the amount by which your modified adjusted gross income exceeds the applicable threshold.10Internal Revenue Service. Net Investment Income Tax For 2026, the thresholds are:
- Single or head of household: $200,000
- Married filing jointly: $250,000
- Married filing separately: $125,000
These thresholds aren’t indexed for inflation, so they reach more taxpayers each year. A large taxable swap can push your income across the line for a single year even if your ordinary income wouldn’t. When you’re planning around a merger that might not qualify for deferral, add this 3.8% on top of the regular capital gains rate.
Reporting the Swap on Your Return
Every stock swap must be reported, taxable or not. Your broker reports the exchange on Form 1099-B, showing the date and proceeds.11Internal Revenue Service. About Form 1099-B, Proceeds from Broker and Barter Exchange Transactions You then report the transaction on Form 8949 and carry the totals to Schedule D.12Internal Revenue Service. About Form 8949, Sales and Other Dispositions of Capital Assets
For a taxable swap, report the proceeds (fair market value of what you received) and your adjusted basis on Form 8949, and let the gain or loss flow to Schedule D. If the basis on your 1099-B doesn’t match your records, enter an adjustment on Form 8949.
Deferred swaps are the trickier case, because the 1099-B may show proceeds that look like a large gain even when you owe nothing (or owe only on boot). List the transaction on Form 8949 and enter an adjustment in column (g) to reduce or eliminate the reported gain. The appropriate adjustment code is “O” per the Form 8949 instructions.13Internal Revenue Service. Instructions for Form 8949 – Sales and Other Dispositions of Capital Assets Attach a statement to your return explaining the non-recognition treatment: identify the reorganization, cite the IRC section you’re relying on (typically Section 354 or 351), state the number and type of shares exchanged, describe any boot, and show your basis calculation in the new stock. Significant holders (5% or more of a publicly traded target, or 1% or more of a non-publicly traded target) face additional reporting obligations under Treasury regulations.
Skipping the reporting is one of the most common mistakes. The IRS sees the 1099-B proceeds and expects a matching entry on your return. If the return is silent, the automated matching system may flag the omission and issue a notice treating the entire amount as taxable gain.