Post-Termination ISO Exercise: Your 90-Day Window Decision

You just left a company — voluntarily or by layoff. Your vested Incentive Stock Options don't move with you. Under federal tax law, you now have a three-month clock to make one of the most financially consequential decisions of your career.

Why 90 days

IRC § 422(a)(2) establishes that an option qualifies as an ISO only if it is exercised within 3 months of the employee's termination date.¹ Exercise after that window and the option loses ISO tax treatment — it becomes an NSO by operation of law, and the spread at exercise is taxed as ordinary income. Most company plans simply expire unexercised options at day 90, meaning you either act or forfeit.

Extended exercise windows: check your plan first

Some companies — mostly later-stage startups that compete on equity-friendly terms — have updated their plans to allow a 1-year, 5-year, or even 10-year post-termination exercise window. Under such a plan, you don't forfeit the options after 90 days, but exercising after 3 months means you've lost ISO status. The options convert to NSOs, and the spread at exercise is ordinary income. This makes the 90-day mark the tax decision deadline even when the plan allows later exercise.

Check your grant agreement or your equity portal (Carta, Shareworks, Morgan Stanley at Work, Fidelity NetBenefits) before making any assumptions about which scenario applies to you.

The core question: exercise, or let expire?

For most departing employees, the choice is binary: pay to exercise within 90 days, or walk away. Three variables drive the answer.

1. Are the options in the money?

ISOs are worth exercising only if the current fair market value (FMV) exceeds your strike price. For public companies, FMV is the market price. For private companies, it's typically the most recent 409A valuation. If strike ≥ FMV, let them expire — never pay to exercise an option with zero or negative intrinsic value.

2. Is the stock liquid?

For public company ISOs, you can exercise and immediately sell if you need to access cash. A same-day "cashless exercise" is a disqualifying disposition — you lose the potential long-term capital gains treatment on the spread, but you avoid AMT and you get cash. This is often the right move when AMT exposure would be punishing.

For private company ISOs, you exercise by writing a check — and you hold paper shares with no guaranteed exit. If the company never achieves a liquidity event at a meaningful price, you've spent real money and potentially paid AMT on gains that never materialize in cash. This is the scenario that results in people owing tens of thousands in AMT on stock they later sell for far less. It happens more often than people expect.

3. Can you afford exercise cost + AMT?

Exercising and holding ISOs past December 31 requires two real cash outlays:

1. Exercise cost: Strike price × shares. At a $5 strike on 10,000 options, that's $50,000 in cash upfront.
2. AMT exposure: The spread (FMV − strike) at exercise is an AMT preference item. If you exercise and hold past year-end, the spread is added to your regular income to calculate tentative minimum tax. For 2026: AMT exemption is $90,100 (single) / $140,200 (MFJ), with phaseout beginning at $500,000 / $1,000,000.⁴

Example: you exercise 10,000 ISOs at a $5 strike when FMV is $20. Spread = $150,000 — an AMT preference item stacked on top of your regular W-2 income. For a typical tech employee already earning $250K–$400K, this can generate an AMT bill in the $20K–$60K range depending on your total income picture, filing status, and remaining exemption. Use the ISO AMT Calculator to model your specific scenario before committing. You need cash to cover both the exercise cost and the potential AMT bill without selling the shares.

If you don't have that cash, a same-day sale (public stock) or letting the options expire (private stock with no liquidity) may be the only realistic paths.

The qualifying disposition math

If you exercise ISOs and hold through the qualifying period, the full gain from strike to sale is taxed as long-term capital gains — not ordinary income. For a high earner, the spread between 37% ordinary income and 23.8% LTCG+NIIT is 13.2 percentage points. On a $300,000 gain, that's $39,600 in tax savings.

The qualifying holding period requires:²

• Hold at least 2 years from the original grant date (not exercise date)
• Hold at least 1 year from the exercise date
• Both must be satisfied before you sell

If you exercise near day 85 of your window, you still need to hold the shares for 12+ months after exercise before selling to preserve ISO treatment. That means holding potentially illiquid or volatile stock for over a year after leaving the company — while also managing a job search or transition. That's real concentration risk you're absorbing in exchange for the tax savings.

Decision flowchart

1. Are your ISOs underwater (strike ≥ FMV)? → Yes: let expire. No: continue.
2. Is the stock illiquid (private) with no near-term liquidity path? → Yes + small or uncertain company: high risk, model carefully before exercising.
3. Do you have cash for exercise cost + estimated AMT? → No: consider exercise financing (companies like Secfi or Quid offer this for late-stage companies), or consider a same-day cashless sale if the stock is public. If neither is viable: let expire or accept NSO treatment if your plan allows extended exercise.
4. Are you willing to hold the shares 12+ months post-exercise? → No: do a same-day cashless sale (public) or exercise-and-sell-quickly (accepts disqualifying disposition, ordinary income on spread). Yes: exercise and hold, with AMT modeled and cash reserved.

Practical steps before day 90

• Find your exact termination date and count 90 calendar days forward. Add it to your calendar with a 60-day reminder — advisors need lead time to model this.
• Log into your equity portal (Carta, Shareworks, E*Trade, Fidelity) and note: number of vested options per grant, strike price per grant, current FMV or 409A, and the expiration date in your grant agreement.
• Read your grant agreement's post-termination clause — specifically look for the phrase "the earlier of..." to see whether your plan expires options at 90 days or allows later exercise.
• Model AMT scenarios using the ISO AMT Calculator before committing to exercise-and-hold for any significant position.
• Talk to a specialist before day 60, not day 88. The full analysis — exercise cost, AMT exposure, multi-year tax projection, concentration risk — takes time to do properly.