What Are Vested Options and How Do They Work?

Vested stock options are the portion of an option grant you’ve earned the right to exercise, meaning you can buy company shares at the strike price locked in when the options were granted, no matter what the stock is worth now. Until options vest, they’re a promise on paper. Once vested, you hold a real legal right to purchase shares at that fixed price, and what you do with that right, and when, carries tax consequences that can swing by tens of thousands of dollars.

What It Means for Options to Be Vested

A stock option grant gives you the potential right to buy a set number of shares at a fixed price. That right doesn’t become yours all at once. Vesting is the process that converts a conditional promise into a guaranteed entitlement. Before vesting, you can’t do anything with the options. After vesting, you decide when and whether to exercise.

Holding vested options is not the same as owning stock. You don’t receive dividends, you can’t vote at shareholder meetings, and you have no equity until you actually exercise and pay the strike price. What you have is a contractual right to buy shares under the terms in your grant agreement, which specifies your strike price, your vesting schedule, and the expiration date after which even vested options become worthless.

How Vesting Schedules Usually Work

Most grants at technology companies and startups follow a four-year schedule with a one-year cliff. During the first twelve months, nothing vests. Hit the one-year mark and 25% of your total grant vests at once. The remaining 75% typically vests in equal monthly installments over the next three years. Some companies vest quarterly instead, but the four-year total is standard.

The cliff exists to protect companies from granting equity to employees who leave quickly. Quit or get terminated at eleven months and you walk away with nothing. Reach month thirteen and you already have a quarter of your options plus one additional month’s worth.

Milestone-based vesting ties options to specific company events or performance targets rather than the calendar. A grant might vest 50% when a product ships and 50% when the company hits a revenue number. This is less common for rank-and-file employees but appears in executive and advisor grants. Time-based or performance-based, the exact conditions live in the grant agreement.

Exercising Vested Options

Exercising means paying the strike price to buy the shares your vested options entitle you to. You submit an exercise notice to your company’s stock plan administrator specifying how many shares you want and how you’ll pay. Three methods are common.

Cash exercise. You pay the full strike price out of pocket and receive the shares. This takes the most cash up front but leaves you holding all the shares.
Cashless, or same-day sale. A broker sells enough shares immediately after exercise to cover the strike price, taxes, and brokerage fees. You keep whatever shares or cash remain. This is the most popular method because you don’t need cash on hand, and it requires a public market for the shares.
Net exercise. The company withholds enough shares from your exercise to cover the strike price and delivers only the net remaining shares. No market sale occurs, which matters at private companies where there may be no public market for the stock.

After payment clears, the company issues shares to your brokerage account or, at a private company, records you as a shareholder on the cap table. From that moment you own actual equity, with exposure to future price changes in both directions.

How Vested Options Are Taxed

The tax treatment of a vested option depends entirely on whether it’s a non-qualified stock option (NSO) or an incentive stock option (ISO). These are two separate regimes, and the difference drives most of the decisions you’ll make.

Non-Qualified Stock Options

NSOs are taxed at exercise. The moment you exercise, the spread between the current fair market value and your strike price counts as ordinary income. Your employer withholds federal income tax, Social Security, Medicare, and applicable state taxes on that spread, just as if it were a bonus on your paycheck.¹

For 2026, the top federal income tax rate is 37%, applying to single filers with income above $640,600 and married couples filing jointly above $768,700.² Add Social Security at 6.2% on earnings up to the annual wage base, Medicare at 1.45%, and the 0.9% Additional Medicare Tax on earnings above $200,000, and a large NSO exercise can face a combined federal rate near 40% before state taxes enter the picture.

If you hold the shares after exercise rather than selling immediately, any later gain or loss is a separate event. Sell within a year and the gain is taxed as short-term capital gains at ordinary rates. Hold for at least a year after exercise and you qualify for long-term capital gains rates, which top out at 20%, with an additional 3.8% Net Investment Income Tax for higher earners.³

Incentive Stock Options

ISOs get better tax treatment if you follow the rules precisely. When you exercise an ISO, you owe no regular federal income tax on the spread at exercise, and your employer doesn’t withhold anything. The tax event is deferred until you sell the shares.⁴

To get the full benefit, you must hold the shares for at least one year after exercise and at least two years after the grant date. Meet both holding periods and your entire profit is taxed at long-term capital gains rates. Fail either test and the sale becomes a disqualifying disposition: the spread at exercise is reclassified as ordinary income, and the preferential treatment is lost.⁵

The $100,000 ISO Limit

There’s a cap that catches people off guard. The tax code limits the aggregate fair market value of stock from ISOs that can first become exercisable in any calendar year to $100,000, measured at the grant date. Options that exceed this threshold are automatically treated as NSOs, regardless of what the grant agreement says. The rule is applied in the order options were granted, so earlier grants get ISO treatment first.⁵

If your company granted you options on 50,000 shares at a $3 strike price, $150,000 worth of stock becomes exercisable as you vest. In any year where more than $100,000 worth vests for the first time, the excess is taxed under NSO rules. You can end up holding a mix of ISO and NSO shares from the same grant without realizing it, which complicates tax time.

The AMT Trap on ISO Exercises

Even though ISOs escape regular income tax at exercise, the spread is an adjustment for the Alternative Minimum Tax. You report the difference between fair market value at exercise and the strike price on Form 6251. For 2026, the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly, with phaseouts beginning at $500,000 and $1,000,000 respectively.²

A large ISO exercise can push you well past those exemption levels and into AMT territory. The AMT rate is 26% on the first $239,100 of AMT income above the exemption for 2026, and 28% above that. If you exercise ISOs and sell the shares in the same calendar year, no AMT adjustment is needed because the regular tax and AMT treatment converge.⁶

AMT paid because of an ISO exercise generates a minimum tax credit you can carry forward using Form 8801. Because the ISO spread is a deferral item rather than a permanent difference, AMT paid now can offset regular tax in later years when you sell the shares and recognize gain for regular tax purposes.⁷

What Happens to Vested Options When You Leave

Unvested options are almost always forfeited the day your employment ends. Any options that haven’t crossed the vesting line are gone. The cliff bites hardest here: leave before the one-year mark and you typically forfeit the entire grant.

For vested options, most grant agreements give you a post-termination exercise period of 90 days from your last day of employment. That window exists because the tax code requires you to exercise an ISO within three months of leaving your job for it to retain its favorable tax treatment.⁵ Companies that want to keep options ISO-eligible set the contractual deadline to match the tax deadline.

If you don’t exercise within that window, your vested options expire and return to the company’s equity pool. You get nothing. This is where people lose real money, especially at private companies where exercising means paying the strike price out of pocket without the ability to immediately sell shares on a public market.

Some companies offer extended post-termination exercise periods of one year, five years, or the full remaining term of the option. The tradeoff is tax treatment: ISOs exercised more than three months after your last day automatically convert to NSOs, which means you lose ISO treatment and owe ordinary income tax on the spread at exercise. More time, different tax math. Grants tied to retirement or disability sometimes carry a 12-month exercise window by default.

What Happens to Vested Options in an Acquisition

When your company gets acquired, your unvested options are in play. What happens depends on whether your grant agreement includes an acceleration clause.

Single-trigger acceleration means all your unvested options vest immediately when the acquisition closes. You don’t need to be laid off or have your role changed. The deal itself is the trigger. Acquirers dislike this arrangement because it removes any incentive for the team to stay after the deal, so single-trigger acceleration is relatively uncommon outside of founder and executive agreements.

Double-trigger acceleration requires two events. First, the company must be acquired. Second, you must be terminated without cause or resign for good reason, such as a significant pay cut or forced relocation, within a set window after the deal closes. This is the structure most investors and acquirers prefer because it keeps the team motivated through the transition while protecting employees who get pushed out. If the company is sold and you keep your job with no material changes, nothing accelerates.

With no acceleration provision at all, the acquirer can choose to assume your options, convert them into options in the acquiring company, or in some cases cash them out. The specific outcome depends on the deal terms.

Early Exercise and the 83(b) Election

Some companies, particularly early-stage startups, allow you to exercise options before they vest. This is called early exercise. You pay the strike price and receive restricted shares that remain subject to the company’s repurchase right. If you leave before vesting is complete, the company can buy back the unvested portion at the original price.

The reason to do this is tax treatment. When you early-exercise at a startup where the strike price equals current fair market value, the spread is zero, so there’s nothing to tax. You lock in that treatment by filing an 83(b) election with the IRS within 30 days of the exercise date. This deadline is absolute, with no extensions and no exceptions.

The 83(b) election tells the IRS you want to recognize income now, at current value, rather than later when the shares vest and could be worth far more. If you file it and the company’s value increases tenfold by the time your shares vest, you owe nothing additional at vesting. All future appreciation is taxed at capital gains rates when you eventually sell. Skip the election and you owe ordinary income tax on the full spread at each vesting date, which at a fast-growing startup can be a devastating surprise.

One boundary worth naming: the 83(b) election applies to restricted stock awards and early-exercised options. It does not apply to standard restricted stock units (RSUs), because RSUs don’t transfer property to you until they vest.⁸

Tax Forms You’ll See

Your company is required to file Form 3921 with the IRS after you exercise incentive stock options and must send you a copy by January 31 of the following year. It reports the exercise price per share, the fair market value on the exercise date, and the number of shares transferred. You’ll use this to calculate your AMT adjustment on Form 6251 and to determine whether you’ve met the required holding periods when you eventually sell.

For NSO exercises, the income appears on your W-2 for the year of exercise, reported as part of your regular wages. The employer handles the withholding, so there’s no separate information return like the 3921.

If you file an 83(b) election for early-exercised options, mail the election to the IRS within 30 days of the exercise, keep a copy with your tax records, and attach a copy to your return for that year.⁸ Missing the 30-day deadline is one of the most expensive mistakes in equity compensation, and the IRS does not grant extensions for late filings.

1
Office of the Law Revision Counsel. 26 USC 83 – Property Transferred in Connection with Performance of Services
2
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
3
Internal Revenue Service. Questions and Answers on the Net Investment Income Tax
4
eCFR. 26 CFR Part 1 – Certain Stock Options
5
Office of the Law Revision Counsel. 26 USC 422 – Incentive Stock Options
6
Internal Revenue Service. 2025 Instructions for Form 6251 – Alternative Minimum Tax – Individuals
7
Internal Revenue Service. 2025 Instructions for Form 8801 – Credit for Prior Year Minimum Tax
8
Office of the Law Revision Counsel. 26 U.S. Code 83 – Property Transferred in Connection with Performance of Services