Vested stock options are employee stock options whose waiting period has passed, giving you the unconditional right to buy shares of your employer’s stock at a preset strike price. Before vesting, options are a conditional promise tied to your continued employment. After vesting, they are earned compensation you can exercise, subject to the deadlines and tax rules that come with the type of option you hold.
What Changes When Options Vest
Every stock option grant comes with a strike price, which is the fixed amount you will pay per share if you decide to buy. Unvested options exist on paper but you cannot use them. You cannot exercise them, sell them, or transfer them, and if you leave the company before they vest, you lose them.
On the vesting date, that changes. You now have a guaranteed right to buy shares at the strike price no matter what the market price is doing. If the stock trades well above your strike, the gap is built-in value. If the stock later drops, your vested right still belongs to you, though deadlines can still take it away if you wait too long to act.
ISOs vs. NSOs
Federal tax law sorts employee stock options into two categories, and knowing which one you hold is the single most important thing to check in your grant agreement. It drives when you owe tax, how much, and at what rate.
Incentive stock options (ISOs) receive favorable treatment under Sections 421 and 422 of the Internal Revenue Code.1Office of the Law Revision Counsel. 26 USC 421 – General Rules Exercising an ISO generally does not trigger ordinary income tax at that moment. The main taxable event is deferred until you sell the shares, although the alternative minimum tax can still apply at exercise.
Non-qualified stock options (NSOs) are governed by Section 83.2Office of the Law Revision Counsel. 26 USC 83 – Property Transferred in Connection With Performance of Services When you exercise an NSO, the spread between the strike price and the fair market value is taxed as ordinary income right away, and your employer withholds tax as it would on regular wages.
How Vesting Schedules Work
Your options vest on a schedule laid out in your grant agreement. Four years total with a one-year cliff is the most common arrangement, but companies structure schedules however they choose.
Time-Based Vesting and the Cliff
Under a time-based schedule, options vest in regular increments, typically monthly or quarterly, over the full vesting period. In a standard four-year grant with monthly vesting after the cliff, you earn one-forty-eighth of the total each month.
The cliff is an initial waiting period during which nothing vests. Leave before the cliff date and you forfeit the entire grant with no partial credit. On the cliff date itself, a large block (often 25% of the total) vests at once, and the remaining options then vest on the regular monthly or quarterly cadence.
Milestone-Based Vesting
Some companies tie vesting to performance targets rather than time, or use both. Options might vest on a revenue goal, a product launch, or a funding round. These terms are specific to your agreement and less standardized than time-based schedules.
Acceleration in an Acquisition
If your company is acquired, unvested options may vest early under an acceleration provision. Single-trigger acceleration vests some or all unvested options when the sale closes. Double-trigger acceleration requires two events: the sale plus your involuntary termination (or resignation for good reason) within a set period afterward, often 9 to 18 months. Not every plan includes acceleration at all, so check your grant agreement and the equity incentive plan before assuming your unvested shares would survive a change of control.
How To Exercise Vested Options
Exercising means paying the strike price to convert your options into actual shares. The strike price was locked in at the fair market value on the grant date. Once you pay it, you are a shareholder.
Three Ways To Pay
A cash exercise, sometimes called exercise and hold, means you pay the full strike price out of pocket and keep the shares. It takes upfront money but lets you hold for future appreciation and potentially for long-term capital gains treatment.
A cashless exercise, or exercise and sell, has your broker exercise and immediately sell the shares on the open market. The proceeds cover the strike price, taxes, and fees, and you get whatever cash is left. No upfront money is needed, but you do not keep any shares.
An exercise and sell to cover splits the difference: the broker sells just enough shares to cover the strike price and withholding, and you keep the rest.
Costs Beyond the Strike Price
Exercising is not free once you get past the strike price itself. Expect brokerage commissions and processing fees, plus tax withholding if you are exercising NSOs. With a cashless or sell-to-cover exercise, those costs come out of the sale proceeds. With a cash exercise, you need enough money on hand to cover both the strike and any withholding your employer requires.
Taxes When You Exercise and Sell
Tax treatment is where option holders most often lose money they did not need to lose. The rules diverge sharply between ISOs and NSOs, and timing can turn the same profit into either capital gains or ordinary income.
NSO Taxes
When you exercise an NSO, the spread between fair market value and strike price is ordinary income for that year. Your employer reports it on your W-2 and withholds federal income tax, Social Security, and Medicare.2Office of the Law Revision Counsel. 26 USC 83 – Property Transferred in Connection With Performance of Services Any further gain when you sell the shares is a capital gain: short-term if you sell within a year of exercise, long-term if you hold longer.
ISO Taxes and the AMT
Exercising an ISO does not trigger ordinary income tax.1Office of the Law Revision Counsel. 26 USC 421 – General Rules The catch is the alternative minimum tax. The exercise spread counts as an adjustment in the AMT calculation, a parallel tax that limits how much high-income filers can shrink their regular tax through deductions and exclusions.3Office of the Law Revision Counsel. 26 USC 56 – Adjustments in Computing Alternative Minimum Taxable Income A big ISO exercise in a single year can produce a real tax bill even when nothing is owed under the regular rules.
For 2026, the AMT exemption is $90,100 for single filers, phasing out at $500,000, and $140,200 for married couples filing jointly, phasing out at $1,000,000.4Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Spreading exercises across multiple tax years is one way to manage AMT exposure.
The ISO Holding Periods
To keep the favorable ISO tax treatment when you sell, you must hold the shares for at least two years from the grant date and at least one year from the exercise date. Both deadlines apply.5Office of the Law Revision Counsel. 26 USC 422 – Incentive Stock Options Sell earlier and you have a disqualifying disposition: the exercise-date spread is reclassified as ordinary income, and any additional gain above the exercise-date value is capital gain.1Office of the Law Revision Counsel. 26 USC 421 – General Rules
When you meet both holding periods, the entire profit qualifies for long-term capital gains rates, which top out at 20% for 2026. That is well below the top ordinary income rate, so the wait can be worth it if you can carry the shares.
The $100,000 ISO Limit
There is a ceiling on ISO treatment. If the total fair market value of stock (measured at grant) covered by ISOs that first become exercisable in a single calendar year exceeds $100,000, the excess is automatically treated as NSOs.5Office of the Law Revision Counsel. 26 USC 422 – Incentive Stock Options With a large grant, part of your options may end up taxed as ordinary income at exercise regardless of holding.
Deadlines After You Leave the Company
When you leave a job, your window to use vested options shrinks fast. Missing the deadline means the equity you already earned disappears.
The 90-Day Window
Most grant agreements give you 90 days after your last day of employment to exercise vested options. Some companies allow longer, occasionally up to 10 years, but 90 days is the common default. If you do not exercise in time, the vested options expire worthless and return to the company’s option pool. Plans generally do not allow extensions.
The ISO Three-Month Rule
For ISOs, federal tax law imposes its own deadline that overrides whatever your plan says. Exercise within three months of leaving and the option keeps its ISO treatment. Exercise later and it is taxed as an NSO, meaning ordinary income tax on the full spread at exercise.5Office of the Law Revision Counsel. 26 USC 422 – Incentive Stock Options Even if your employer offers a longer post-termination window, the ISO benefit is gone at three months.
Termination for Cause
Many equity plans cancel both vested and unvested options if you are terminated for cause, meaning serious misconduct such as fraud, theft, or breach of a non-compete. In that scenario, you can lose everything regardless of tenure. Your grant agreement defines whether and how this applies.
Absolute Expiration
Every option has a maximum life independent of employment. Federal regulations cap ISOs at 10 years from grant, dropping to five years if you own more than 10% of the company’s voting stock at the time of the grant.6eCFR. 26 CFR 1.422-2 – Incentive Stock Options Defined NSO terms are set by the plan, and 10 years is standard. Regardless of what remains on your post-termination clock, options that hit their absolute expiration date are gone.
A Note on Early Exercise and 83(b)
Some companies, especially early-stage startups, let you exercise options before they vest. That is a separate path from exercising vested options and comes with its own tax mechanic: a Section 83(b) election filed with the IRS within 30 days of the early exercise, which asks the IRS to tax the shares based on today’s value rather than the value at each future vesting date.7Internal Revenue Service. Form 15620 – Section 83(b) Election Miss the 30-day window and you are taxed at each vesting date instead, often on much higher values if the company has grown.2Office of the Law Revision Counsel. 26 USC 83 – Property Transferred in Connection With Performance of Services If you leave before vesting, you forfeit the unvested shares and cannot recover the tax already paid. Because the deadline is short and the consequences are permanent, many employees consult a tax professional before deciding.