Stock Options in Your Employment Agreement: ISOs, NSOs, and What Matters

Stock options are the primary equity vehicle at early and mid-stage startups, and they work very differently from the RSUs that large public tech companies use. If your employment agreement includes an option grant, there are several things you need to understand before you sign — and several more you need to understand before you ever decide to exercise.

ISOs vs NSOs: The Tax Difference

Stock options come in two main types, and the tax treatment is meaningfully different.

Incentive Stock Options (ISOs) are available only to employees (not consultants or board members) and are subject to specific IRS rules. The key benefit: if you exercise and hold your ISO shares for at least two years from the grant date and one year from the exercise date, the gain is taxed at long-term capital gains rates rather than ordinary income rates. Capital gains rates are generally lower than ordinary income rates — the difference can be significant on a large grant.

The catch: ISOs may trigger Alternative Minimum Tax (AMT) at exercise, even before you sell the shares. The spread between the strike price and the fair market value at exercise is an AMT preference item. In a year when a startup's stock price has risen significantly from your strike price, exercising ISOs can create a substantial AMT liability — even if you haven't sold a single share and have no cash from the transaction.

Non-Qualified Stock Options (NSOs or NQSOs) don't have the ISO holding requirements or AMT implications. When you exercise an NSO, the spread between the strike price and the fair market value at exercise is taxed as ordinary income in the year of exercise — regardless of whether you sell the shares. This is simpler but generally less tax-favorable than the ISO regime for employees in high tax brackets.

The type of option in your grant document matters. Most startup grants to employees are ISOs up to the statutory cap ($100,000 in ISOs that first become exercisable in any calendar year); amounts above the cap are automatically treated as NSOs.

The Strike Price and 409A Valuation

Every option grant includes a strike price — the price per share you'll pay to exercise the option. The strike price must be set at the fair market value of the company's shares on the grant date, as determined by an independent 409A valuation.

A 409A valuation is an appraisal of the company's common stock value, conducted by an independent firm and required periodically under IRS rules. The company's last 409A valuation is the benchmark against which your strike price is set.

What the strike price tells you: if the 409A valuation was $1.00 per share and your strike price is $1.00, your options are at-the-money. If the company subsequently raises a Series B at $5.00 per share (for preferred stock), your options may be in-the-money — but the common stock value (which is what your 409A covers, not preferred) may still be significantly below the preferred price due to liquidation preferences and other preferred stock rights.

Ask for the most recent 409A valuation and confirm your strike price matches it. Also ask: what's the current preferred stock price (last round)? And what's the current 409A common stock value? Understanding the relationship between these numbers helps you assess what your options might actually be worth.

The 90-Day Post-Termination Problem

Most stock option agreements include a post-termination exercise window of 90 days. This means: if you leave the company for any reason (resignation, layoff, or otherwise), you have 90 days to exercise your vested options before they expire permanently.

Exercising options costs real money. If your strike price is $1.00 per share and you have 100,000 vested options, exercising them costs $100,000. If the company's shares aren't publicly tradeable (because it's a private startup), you can't immediately sell the shares to cover the exercise cost. You have to come up with the cash, hold illiquid shares, and hope the company eventually has a liquidity event.

Many employees simply let their options expire unexercised because they can't afford the exercise cost within 90 days. This is a known, widespread problem — and it means a significant portion of the compensation that employees believe they've "earned" is actually lost on termination.

Extended Exercise Windows

Some companies have adopted extended post-termination exercise windows as an employee-friendly policy — typically 1 year, 5 years, or even the full 10-year life of the option. Extended windows give departing employees more time to arrange financing for exercise, wait for a liquidity event, or make a more deliberate decision.

If the company you're joining hasn't explicitly addressed the post-termination exercise window in your offer materials, it's worth asking. Most startups can extend the window at relatively low cost. It's a benefit that matters most precisely when you're vulnerable — when you're leaving — and it's a legitimate negotiating point.

If the company offers extended windows, note that they may convert ISO treatment to NSO treatment (the ISO holding period requirements become harder to satisfy). This is a trade-off worth understanding but not necessarily a reason to avoid extended windows.

Early Exercise and the 83(b) Election

Many startup option grants include an early exercise provision — the ability to exercise options before they've vested. If you early exercise, you purchase unvested shares that are subject to a repurchase right: if you leave before the shares vest, the company can repurchase the unvested portion at the original strike price.

The potential benefit of early exercise is tax optimization. If you exercise when the 409A valuation is low (at or near the strike price), there's little or no taxable spread at exercise. The clock on your capital gains holding period starts earlier. If the company succeeds and the stock value increases significantly, the appreciation over your long holding period is taxed at capital gains rates rather than ordinary income rates.

To lock in this treatment, you must file an 83(b) election with the IRS within 30 days of early exercise. Missing this deadline forfeits the election permanently. The election is a one-page form submitted to the IRS, and most startup lawyers can explain the mechanics. If you're considering early exercise, the 83(b) deadline is non-negotiable.

What to Check in Your Option Grant

Before signing your option grant:

• ISO or NSO: Confirm the type.
• Strike price: Confirm it matches the most recent 409A valuation.
• Grant date: Confirms when the vesting schedule starts.
• Vesting schedule: Cliff date and post-cliff vesting frequency.
• Post-termination exercise window: 90 days, or something longer?
• Early exercise option: Is it available? If yes, understand the 83(b) election requirement.
• Acceleration provisions: Any change-of-control or termination-triggered acceleration?

The Bottom Line

Stock option grants can be enormously valuable or largely theoretical depending on the exercise window, the 409A valuation at exercise, and the company's ultimate outcome. Before accepting an offer with an option grant, paste your option grant and employment agreement into dott.legal for a free AI risk analysis. For situations involving early exercise decisions, a significant AMT question, or a career move from a startup, attorney-validated review is $349 with 24-hour turnaround.