In a merger that pays you half cash and half stock, the tax implications split cleanly in two: the cash side is taxable now, and the stock side is deferred. Under IRC Section 356, you recognize gain up to the amount of cash received (called “boot”), while the acquiring company’s stock carries your old cost basis forward, adjusted for what you already recognized. The overall deal can still qualify as a tax-deferred reorganization under Section 368 even though you write a check to the IRS for the cash portion.
How the Cash Portion Gets Taxed
Section 356 sets the rule that governs a 50/50 cash and stock merger. You recognize gain, but only up to the lesser of (a) your total realized gain on the exchange or (b) the cash you received. Losses aren’t recognized at all in these exchanges; a built-in loss survives inside the basis of your new shares.
An example makes the mechanics concrete. Say you paid $30,000 for your target company shares. The deal delivers $50,000 in cash and $50,000 of the acquirer’s stock, for $100,000 total. Your realized gain is $70,000. Because the cash ($50,000) is less than that, you recognize $50,000 this year. The remaining $20,000 of gain stays deferred inside the new shares.
Flip the numbers and the cap moves. If your original basis had been $60,000, your realized gain would be only $40,000. You’d recognize $40,000, not $50,000, because the statute taxes the gain limited by the boot, not the boot itself. That distinction matters: the cash is not taxed dollar for dollar. It only sets a ceiling.
Whether the recognized gain is long-term or short-term depends on how long you held the original target company shares before the closing, not on the merger date itself.
When the Cash Is Taxed as a Dividend Instead
Section 356 contains a wrinkle worth knowing about. If the cash payment has “the effect of the distribution of a dividend,” part of your gain can be recharacterized from capital gain to dividend income, up to your ratable share of the corporation’s accumulated earnings and profits.
In Commissioner v. Clark, the Supreme Court adopted a test that treats the cash as though you first received all stock and then immediately redeemed some of those shares for cash. If that hypothetical redemption would qualify as an exchange under Section 302 rather than a dividend, the boot keeps capital gain treatment. For a minority shareholder in a public company, that hypothetical redemption almost always passes: your ownership percentage drops far more than 20%, and you end up holding well under 50% of the vote. Capital gain treatment is the norm.
Dividend recharacterization tends to bite in closely held companies, where a shareholder’s percentage stake before and after doesn’t shift much. Even then, qualified dividends are taxed at the same preferential rates as long-term capital gains for most taxpayers, so the practical difference often reduces to whether the amount can offset capital losses. Dividends can’t.
The Rates You’ll Actually Pay
Long-term capital gains for 2026 fall into three federal brackets:
- 0% on taxable income up to $49,450 (single) or $98,900 (married filing jointly).
- 15% from those thresholds up to $545,500 (single) or $613,700 (joint).
- 20% above those amounts.
Short-term gains on shares held one year or less are taxed at ordinary income rates, which reach 37% in 2026.
On top of that, a 3.8% net investment income tax applies to capital gains once modified adjusted gross income exceeds $200,000 (single) or $250,000 (joint). A large merger gain can push you across that threshold on its own, taking the effective top federal rate on long-term gains to 23.8%. The surtax applies to the smaller of your net investment income or the amount by which MAGI exceeds the threshold.
Most states with an income tax also tax capital gains, and a few tax them at ordinary rates rather than a preferential rate. State liability can range from roughly 3% to over 13%, depending on where you live.
Basis and Holding Period of Your New Shares
The stock you receive doesn’t come in at market value for tax purposes. Under IRC Section 358, its basis equals your old basis, minus the cash received, plus the gain you recognized.
Applying that to the first example: $30,000 old basis, minus $50,000 cash, plus $50,000 recognized gain, equals $30,000. Your new stock is worth $50,000 but has a basis of $30,000. The $20,000 gap is exactly the piece of your original gain that stayed deferred. When you eventually sell those shares at $50,000, that $20,000 comes out as gain then.
Holding period tacks. Under IRC Section 1223, because the new shares take a substituted basis from the old ones, the time you held the target’s stock counts toward the new stock’s holding period. If you owned the target for three years before the deal closed, the acquirer’s stock is treated as three years old from day one. That’s what makes the deferred gain almost certain to qualify for long-term treatment when you sell.
If you bought your target shares in multiple lots at different prices and dates, basis has to be allocated lot by lot. Treasury regulations require tracing each old share to the new shares received for it, allocating basis by fair market value when one old share produces multiple new shares. You can designate the pairing yourself if it’s not otherwise identifiable, but you have to do it consistently and at the time of the exchange. Skip the designation and you lose the ability to specifically identify shares when you sell later.
Reporting the Merger on Your Return
Your broker will send a Form 1099-B showing the cash proceeds. The catch: brokers frequently report the full cash amount without adjusting cost basis for how a reorganization actually works. Taking the 1099-B at face value can leave you reporting too much or too little.
The transaction goes on Form 8949, with totals flowing to Schedule D. When the broker’s basis is wrong, enter adjustment code “B” in column (f). Correct the basis in column (e) or enter an adjustment in column (g), depending on whether basis was reported to the IRS.
The acquiring company is required to file Form 8937, which reports organizational actions affecting the basis of your securities. That form is your primary reference for the substituted basis calculation and should be posted on the acquirer’s investor relations page. If the deal offered elections between more cash or more stock, elections are typically subject to proration when one option is oversubscribed. Your actual mix after proration is what drives your tax outcome, not what you asked for. The Form 8937 and closing documents will show the ratio you actually received.
Estimated Tax Payments to Avoid a Penalty
A large recognized gain from a merger creates a tax bill that ordinary paycheck withholding won’t cover. The IRS generally requires estimated payments if you’ll owe at least $1,000 after withholding and credits, and your withholding won’t reach the smaller of 90% of your current-year tax or 100% of last year’s tax (110% if your prior-year AGI exceeded $150,000).
Timing matters. If the deal closes early in the year, you can spread the payments across the quarterly deadlines: April 15, June 15, September 15, and January 15 of the following year. If it closes later, you may need a single lump payment by the next quarterly due date. When the gain lands in one quarter rather than evenly across the year, the annualized income installment method on Form 2210 can reduce or eliminate the underpayment penalty by tying the calculation to when you actually received the income.
Pitfalls Worth Watching
Fractional shares are the most commonly missed piece. When the exchange ratio produces a fraction, you usually receive cash in lieu. That cash-in-lieu is generally treated as if you received the fractional share and immediately sold it, producing a small gain or loss separate from the boot calculation. It still belongs on Form 8949.
“Tax-free reorganization” is a phrase that misleads people every year. The reorganization is tax-deferred at the corporate level and for the stock portion of your consideration. The cash you receive is not. Every dollar of boot triggers gain recognition up to your realized gain, and reporting that gain is on you, not on the companies.
Keep your records. You’ll need your original purchase documentation, the merger terms, the Form 8937, any proration results, and your basis worksheet. The deferred gain sitting inside your new shares may not surface for years, and rebuilding the numbers later is far harder than saving them now.
One boundary worth noting: if you owned at least 5% (by vote or value) of a publicly traded target, or at least 1% of a non-publicly traded target, Treasury Regulation 1.368-3 requires you to attach a “significant holder” statement to your return for the year of the reorganization, disclosing the shares surrendered, consideration received, and basis calculations. Retail shareholders in public companies are almost always below that threshold; holders of substantial stakes in smaller companies should check.