Startup Acquisition Taxes: Cash, Buyer Stock and Your Shares

How are startup acquisition taxes figured on each part of the deal?

Each part of the price is taxed by its own rule. Cash for your shares is taxable gain in the closing year. Buyer stock is deferred only when the deal qualifies as a tax-free reorganization under section 368, and the deal's structure decides that, not you.

A case stops being simple when the gain is large, the shares came in blocks bought at different prices or times, part of the price comes later, you claim QSBS, you move states before closing, or you live outside the US. Gather the merger agreement, the funds-flow or payment statement, your cap table entries, purchase and option exercise records, any 83(b) election, and the company's QSBS statement if it gave one.

How is an all-cash acquisition of my shares taxed?

When the buyer pays cash for your shares, you have a capital gain equal to the cash minus your basis in the shares. Shares held more than one year give long-term gain, taxed at up to 20% federally (IRS Topic 409), plus the 3.8% net investment income tax once your modified adjusted gross income passes $200,000 single or $250,000 married filing jointly.

A cash merger is taxed the same way as a direct sale of your shares. Watch for pay disguised as price: amounts that depend on you staying employed are usually wages, not sale proceeds. See earnout and retention payments. Price held back in escrow has its own timing rules; see escrow and holdback payments.

Is a stock-for-stock acquisition taxable?

A stock-for-stock acquisition is not taxed at closing if it qualifies as a reorganization. Section 354 then says no gain or loss is recognized on shares exchanged solely for stock of a party to the reorganization. The merger agreement usually states the intended tax treatment; read that clause.

Whether a deal qualifies depends on rules about the company and the deal, not on anything you file:

• Continuity of interest. A substantial part of the price must be buyer stock (26 CFR 1.368-1(e)). The regulation's examples treat 40% buyer stock as enough and 25% as too little. When the contract fixes the consideration, the stock is valued just before signing.
• Deal form. A reverse triangular merger, where the buyer's subsidiary merges into your company, needs former shareholders to exchange shares carrying control, at least 80% of the voting power, for the buyer's voting stock (section 368(a)(2)(E) and (c)). A direct stock-for-stock acquisition must be solely for voting stock.

If the deal does not qualify, the buyer stock is taxed like cash at its value on the closing date. That can mean tax due on shares you cannot sell yet. Ask before signing whether the buyer stock comes with sale restrictions.

In a cash and stock merger, how much of the cash is taxed?

In a qualifying cash and stock merger, your gain is taxed only up to the cash and other property you receive (section 356(a)). If your total gain is smaller than the cash, only the gain is taxed. A loss is not allowed in the exchange.

Two traps follow from the regulations:

• Share-by-share math. Unless the deal terms say otherwise, the cash is spread across each share you surrender by value, and gain is figured share by share (26 CFR 1.356-1(b)). A block bought at a high price cannot soak up gain on a cheap founder block.
• Dividend treatment. If the cash has the effect of a dividend, part of the taxed amount can be a dividend instead of capital gain (section 356(a)(2)). This is rare for a shareholder who gives up all shares for a mix of cash and buyer stock, but it is fact-dependent.

What basis and holding period do my new buyer shares get?

Your buyer shares take the basis of the shares you gave up, minus the cash received, plus the gain you were taxed on (section 358(a)). The holding period of your old shares carries over to the new ones (section 1223(1)), so long-term status is kept.

Basis follows blocks. Each new share takes basis from the old shares it replaces, matched as closely as possible to shares acquired on the same date at the same price (26 CFR 1.358-2). Keep a schedule by block: founder shares, exercised options and later purchases each have their own basis and date.

The issuer of the shares reports how the deal affects basis on Form 8937, often posted on its public website. The Form 8937 instructions give a deadline of 45 days after the action or, if earlier, January 15 of the next year.

Does QSBS still apply in a stock sale, a merger or an asset sale?

QSBS can apply in all three, but each works differently. Section 1202 excludes gain from a sale or exchange of qualifying stock by a holder other than a corporation. Whether your shares qualify, and your tier and cap, are covered in QSBS for founders and early employees.

The holding-period clock matters. If closing comes before your shares reach the period they need, a section 1045 rollover may defer the gain. Many states do not follow the exclusion; see state tax on QSBS gains.

What happens to my stock options and unvested shares when the company is acquired?

The deal can cash out, assume, replace or cancel your options. Each outcome is taxed differently:

Cash-outs are often withheld as supplemental wages at a flat 22%, rising to 37% on supplemental wages above $1 million in the year (Publication 15). Flat withholding can fall short of your actual rate. The employer also withholds 0.9% Additional Medicare Tax on your wages above $200,000 in the year. For tax on exercising options before the deal, see exercising startup stock options.

Unvested shares depend on the 83(b) election. With a timely 83(b), you are treated as owning the shares, so payment for them is sale proceeds. Without one, if the shares are sold in an arm's-length deal while still unvested, the amount received minus what you paid is compensation (26 CFR 1.83-1(b)). If buyer shares with new vesting replace them, get the intended treatment in writing. See 83(b) elections on your return.

Shares from exercised incentive stock options that are sold for cash within 2 years of grant or 1 year of exercise are a disqualifying disposition: the spread at exercise becomes wages and only the rest is capital gain (section 422(a)). Exchanging them for buyer stock in a qualifying reorganization is not a disposition (section 424(c)(1)). See exercising startup stock options.

What is the golden parachute rule, and why do stockholders vote on it?

The golden parachute rule taxes very large deal-related pay to officers, larger shareholders and highly paid people. If their payments contingent on the change in control reach three times their "base amount", an average of recent years' pay, the amount above one times the base is an excess parachute payment (section 280G). The recipient owes a 20% excise tax on it (section 4999), and the company loses its deduction.

A private company can exempt the payments with a shareholder vote. More than 75% of the voting power must approve after adequate disclosure, not counting the shares of the people being paid (26 CFR 1.280G-1, Q&A-7). The vote must decide whether the payments are made, so the people affected usually waive them unless the vote passes. That is why stockholders receive a disclosure and ballot before closing. A company eligible to be an S corporation, ignoring the bar on nonresident alien shareholders, is exempt without a vote (section 280G(b)(5)(A)(i)). The company side is covered in tax clean-up before selling your startup.

When is the tax due, and do I need estimated payments after closing?

Tax on cash received at closing belongs to the closing year. Sale proceeds generally have no income tax withheld, so the tax is paid through estimated payments or with the return. The exception is backup withholding at 24%, which a paying agent can take if you do not give it your taxpayer identification number (Form 1099-B instructions). Publication 505 says the penalty is avoided if withholding and estimated payments cover 90% of this year's tax or the prior-year target: 100% of last year's tax, or 110% if last year's adjusted gross income was above $150,000 ($75,000 married filing separately).

Paying the prior-year target avoids the federal penalty but still leaves a large balance due with the return. If the deal closes late in the year, the annualized income installment method bases each payment on income received so far, so the gain can be covered by the payment after closing instead of earlier ones; you then file Form 2210 with the return. Quarterly due dates are April 15, June 15, September 15 and January 15, 2027. State estimated tax is separate; see state tax on QSBS gains, and if you are moving, moving before selling startup shares.

Which forms will I get, and where does the sale go on my return?

Share sales go on Form 8949 and Schedule D; option cash-outs and deal bonuses go on your W-2 and the wages line.

Report the sale on Form 8949 even without a 1099-B; long-term sales with no form use box F. For a QSBS exclusion, report the sale as usual, enter code Q in column (f) and the excluded amount as a negative number in column (g).

In a reorganization, a holder of at least 1% of a privately held target's stock is a "significant holder" and must attach a statement to the return for the exchange year (26 CFR 1.368-3(b)). It lists the parties, the date, and the value and basis of the shares exchanged.

Example

All figures are in US dollars and illustrative.

Cash and buyer stock in a qualifying merger

A founder's shares have a basis of $100,000. In a qualifying merger, they receive $1,000,000 in cash and buyer stock worth $3,000,000.

• Total gain: $4,000,000 − $100,000 = $3,900,000.
• Taxed now: the lesser of the gain and the cash, so $1,000,000, long-term capital gain because the shares were held more than one year.
• Buyer stock basis: $100,000 − $1,000,000 cash + $1,000,000 gain taxed = $100,000. The holding period carries over.
• Deferred: $2,900,000, taxed when the buyer stock is sold.

All cash with QSBS

A founder's shares were issued in 2019 for $20,000 and are sold for $2,000,000 after seven years. The gain is $1,980,000. If the shares qualify, the older-stock rules can exclude all of it federally, because it is under the $10,000,000 cap. California or another state may still tax the gain; see the state guide below.

Options cashed out

An employee holds 20,000 vested options. The deal cancels them for $5 each, the price per share minus the exercise price. The $100,000 is wages on the W-2. If the employer withholds at the flat 22% rate, $22,000 is withheld, which can be less than the tax due at the employee's actual rate.

Different for you?

• Part of the price is held in escrow or a holdback: see escrow and holdback payments.
• You get an earnout or retention package: see earnout payments after a startup sale.
• You are not sure your shares qualify for QSBS, or which cap applies: see QSBS for founders and early employees.
• Your state may tax gain excluded federally: see state tax on QSBS gains.
• You plan to move states before closing: see moving before selling startup shares.
• You live in Canada: see Canadian founders selling US startup shares.
• You run the company and want to know what diligence will find: see tax clean-up before selling your startup.
• A small owner-run business is choosing an asset or stock sale: see selling your business.
• Your gain is large, your shares are in several blocks, or the deal mixes cash, stock and later payments: get individual tax help before closing.