A cashless exercise of stock options or RSUs lets you convert your equity award into shares or cash without writing a check. Your employer’s designated broker sells just enough shares at the current market price to cover the purchase cost and required tax withholding, then delivers the rest to your brokerage account. It’s the default path most employees take, and it works, but the tax reporting has a few traps worth knowing before you file.
What Happens During a Cashless Option Exercise
Three things happen almost simultaneously. You tell the broker to exercise your options, the broker sells enough of the resulting shares on the open market, and the sale proceeds pay everything you owe before the remaining shares land in your account.
Those proceeds cover three costs. The strike price your option agreement says you pay per share. Mandatory tax withholding on the ordinary income you realize at exercise. And any brokerage commissions or transaction fees. The broker calculates the minimum number of shares needed to cover all three, sells those, and deposits whatever is left as your net shares.
Your holding period for those net shares starts the day after the exercise date. That start date decides whether a future sale gets short-term or long-term capital gains treatment.
How Sell-to-Cover Works for RSUs
RSUs work differently because there is no strike price. When RSUs vest, the company simply delivers shares to you, and the full market value of those shares counts as taxable compensation. The “cashless” piece is really just a sell-to-cover arrangement for the tax bill.
The broker withholds a portion of your vesting shares, sells them, and sends the cash to your employer to cover income and payroll tax. The federal supplemental wage withholding rate is a flat 22% on compensation up to $1 million and 37% on anything above that threshold within the same calendar year.1Internal Revenue Service. Publication 15 – Employer’s Tax Guide Your employer also withholds Social Security tax at 6.2% on wages up to the $184,500 base for 2026, plus Medicare tax at 1.45% with no cap.2Social Security Administration. Contribution and Benefit Base
The remaining shares are deposited into your account. Your cost basis for those shares is the fair market value on the vesting date, which is also the amount your employer reports as compensation on your W-2.
Ordinary Income at Exercise or Vesting
Whether you hold options or RSUs, a cashless transaction creates immediate ordinary income. For nonqualified stock options, the taxable amount is the spread: market price minus strike price, multiplied by the number of shares exercised. For RSUs, it’s the full market value of every share that vests. Both amounts flow into your W-2 as wages.
For nonqualified options specifically, the income appears in Box 12 of your W-2 under Code V.3Internal Revenue Service. Announcement 2002-108 RSU income has no dedicated Box 12 code. It’s folded into your total wages in Box 1 and into your Social Security and Medicare wages in Boxes 3 and 5. Some employers voluntarily label RSU income in Box 14, but they’re not required to.
This income is subject to federal and state income tax, Social Security tax up to the annual wage base, and Medicare tax. The withholding done during the cashless transaction is meant to cover these obligations, but it often falls short.
Why Cashless Usually Breaks ISO Treatment
If your options are incentive stock options rather than nonqualified options, a cashless exercise creates a problem most people don’t see coming. ISOs get favorable tax treatment only if you hold the shares for at least two years after the grant date and one year after the exercise date.4Office of the Law Revision Counsel. 26 U.S. Code 422 – Incentive Stock Options A same-day cashless exercise violates both holding periods because you’re selling on the day you acquire.
That makes the transaction a disqualifying disposition. The spread between your strike price and the market price on the exercise date gets taxed as ordinary income, exactly like a nonqualified stock option. You lose the ISO’s capital gains advantage entirely. For that reason, the cashless approach often makes less sense for ISOs than paying cash to exercise and holding the shares long enough to qualify.
The Cost Basis Trap on Your 1099-B
This is where most people overpay their taxes, sometimes by a lot. When your broker reports the sale on Form 1099-B, the IRS prohibits the broker from including the compensation income you already recognized as part of the cost basis.5Internal Revenue Service. About Form 1099-B, Proceeds from Broker and Barter Exchange Transactions For nonqualified options, the 1099-B reports your basis as only the strike price, not the full fair market value at exercise. For RSUs, the basis may be reported as zero or omitted entirely, because RSU shares aren’t covered by the IRS’s cost basis reporting rules the same way purchased shares are.
Here’s why that matters. Say your RSUs vest at $50 per share and you later sell at $55. Your actual gain is $5 per share. But if the 1099-B reports your basis as $0, the IRS sees a $55 gain. File without adjusting the basis and you pay tax again on income you were already taxed on through your W-2. For short-term sales, that mistake can nearly double the tax bill on the transaction.
To fix it, report the correct adjusted basis on Form 8949. The adjustment equals the compensation income already included on your W-2. Keep your exercise confirmations, vesting statements, and W-2 forms together so you can prove the adjustment if the IRS ever asks.
Withholding at 22% Usually Isn’t Enough
The flat 22% federal withholding on supplemental wages is a withholding rate, not your actual tax rate. If you’re in the 32% or 35% bracket, that 22% won’t come close to covering your federal income tax on the gain. State taxes widen the gap. Plenty of employees discover the shortfall the following April.
You generally must make estimated tax payments if you expect to owe at least $1,000 after subtracting withholding and credits, and your total withholding will be less than 90% of your current-year tax or 100% of your prior-year tax (110% if your AGI was over $150,000).6Internal Revenue Service. Large Gains, Lump-Sum Distributions, Etc. One practical workaround: increase the federal withholding on your regular paycheck for the rest of the year. The IRS treats paycheck withholding as paid evenly throughout the year, which avoids underpayment penalties even if you make the adjustment late in the year. Quarterly estimated payments don’t get that treatment; miss the quarter in which the income landed and a penalty can still apply.
Capital Gains When You Sell the Net Shares
The net shares sitting in your brokerage account after a cashless exercise aren’t done with taxes. When you sell them later, you’ll owe capital gains tax on any appreciation above your cost basis. That basis is the fair market value on the exercise date for options, or the vesting date for RSUs.
Sell within one year of that date and the gain is short-term, taxed at ordinary income rates. Hold longer than one year and it qualifies for the lower long-term capital gains rate.7Internal Revenue Service. Topic No. 409, Capital Gains and Losses If the stock drops below your basis and you sell at a loss, you can deduct that loss against other gains or up to $3,000 of ordinary income per year.
Extra Taxes for Higher Earners
Large exercises and vests can push your income into territory where extra taxes apply.
The Additional Medicare Tax adds 0.9% on wages above $200,000 for single filers or $250,000 for married couples filing jointly.8Internal Revenue Service. Topic No. 560, Additional Medicare Tax Your employer withholds this tax once your total wages for the year cross $200,000, regardless of filing status. If you’re married filing jointly and your combined wages don’t actually exceed $250,000, you can claim the excess withholding back on your return. If they do exceed the threshold, you may owe more than what was withheld.
The Net Investment Income Tax is a separate 3.8% surtax on investment income, including capital gains from selling your shares after the exercise or vesting. It applies when your modified adjusted gross income exceeds $200,000 for single filers or $250,000 for joint filers.9Internal Revenue Service. Net Investment Income Tax The ordinary income from your options or RSUs doesn’t count as net investment income itself, but it inflates your AGI and can pull capital gains from other investments into the NIIT zone.
Wash Sale Risk Around Vesting Dates
If you sell company shares at a loss within 30 days before or after an RSU vest or stock option exercise, the wash sale rule can disallow your loss. The IRS treats the vest or exercise as an acquisition of substantially identical stock.10eCFR. 26 CFR 1.1091-1 – Losses From Wash Sales of Stock or Securities The 61-day window (30 days before the sale through 30 days after) means regular monthly or quarterly vesting schedules create overlapping wash sale traps almost continuously.
The disallowed loss isn’t gone permanently. It’s added to the cost basis of the newly acquired shares, so you recover it when you eventually sell those. But if you were counting on the loss to offset a gain in the current tax year, you’ll be disappointed. The reliable way to manage this is to track your vesting schedule and avoid selling company shares at a loss inside the 61-day window.
Alternatives to Going Cashless
Cashless is popular because it costs nothing upfront. Two other approaches can produce better outcomes depending on your cash position and risk appetite.
Cash Exercise and Hold
You pay the strike price and tax withholding from your own pocket and keep every share. More shares mean more upside if the stock climbs. The downside is that you’re tying up cash in a single stock that also happens to be your employer. If the company stumbles, your shares lose value at the moment your job may also be at risk. This makes sense only if you have enough liquid savings to absorb the outlay and genuine conviction in the stock’s long-term trajectory.
Net Exercise or Stock Swap
A net exercise reduces the number of shares delivered to you by the amount needed to cover the strike price, with no open-market sale. You don’t need cash and nothing trades on the exchange. Some plans also allow a stock swap, where you surrender previously owned shares with a value equal to the strike price. With a swap, surrendered shares keep their original cost basis and holding period, which can be useful if those shares already qualified for long-term capital gains treatment. Not every plan offers these methods, so check your equity plan documents.