You've spent years at a startup, accumulated vested stock options, and you're leaving. Before your last day, you need to understand one thing: most vested options come with a hard expiration date — and the countdown starts the moment your employment ends.
Two different things happen to your options when you leave, depending on whether those options have vested. Here's the complete breakdown.
Unvested Options: They're Forfeited on Your Last Day
When you leave a startup, unvested options don't follow you — they revert immediately to the company's option pool. If you're on a standard 4-year vesting schedule with a 1-year cliff, any options that haven't vested by your last day are gone. It doesn't matter how close you were to the next vesting milestone.
Key concept
Unvested ≠ earned. Vesting is the schedule by which the company grants you the right to purchase shares over time. Until an option vests, you haven't earned it under the terms of the agreement — so it reverts when employment ends.
The only exception is an acceleration clause in your grant agreement. Single-trigger acceleration automatically vests some or all of your unvested options when a specific event occurs — typically an acquisition or change of control. Double-trigger acceleration requires two events: a change of control plus an involuntary termination (being laid off, not resigning). If your agreement includes either clause, read it carefully before you leave — it may change your picture significantly.
Vested Options: You Have a Window to Act
Here's what most people get wrong: vested options are not the same as shares. A vested stock option is the right to purchase shares at your strike price. Until you exercise — pay the strike price to complete the purchase — those shares are not yours.
When you leave, your vested options don't become worthless immediately. You have a defined amount of time after your departure to decide whether to exercise them. This window is called the post-termination exercise period, or PTEP. If you don't exercise within your PTEP, the options expire permanently — they cannot be recovered or reinstated.
The Post-Termination Exercise Period (PTEP)
The post-termination exercise period is the window, defined in your equity plan documents, during which you can exercise vested options after leaving. The standard PTEP is 90 days. Most early-stage equity plans are written this way, and 90 days is also the IRS-defined deadline for incentive stock options (ISOs) to maintain their favorable tax treatment. Some companies set shorter windows — 30 or 60 days. Others are more generous with 1, 5, or even 10 years.
⚠️ The 90-day clock starts on your last day of employment — not on the day you receive a severance agreement, not on the day you make a decision, and not on the day you realize you had options. Your last day. The company will not typically send a reminder when the window is closing.
Your PTEP is specified in your individual option grant agreement and the company's equity incentive plan. These are the authoritative documents — not what HR said verbally, not what a colleague told you. Request copies before you leave.
ISOs vs. NSOs: Why the Distinction Matters After You Leave
Stock options come in two tax-distinct types: incentive stock options (ISOs) and non-qualified stock options (NSOs). Most startup employees receive ISOs — but not always, and sometimes a mix. The difference has real consequences when you leave.
ISOs (Incentive Stock Options): To preserve ISO tax treatment, you must exercise within 90 days of your last day. After 90 days, ISO options automatically convert to NSOs for tax purposes — even if your company's stated PTEP is longer than 90 days. ISOs exercised within the 90-day window don't generate ordinary income at exercise. The spread (fair market value minus your strike price) is instead a preference item for Alternative Minimum Tax (AMT) purposes.
NSOs (Non-Qualified Stock Options): Ordinary income tax is due on the spread at exercise — the moment you exercise, not when you sell. If the company's current 409A-based fair market value is $15 and your strike price is $2, you owe ordinary income tax on $13 per share the year you exercise, whether or not you can sell the shares.
For more on this topic
For a deeper walkthrough of how ISOs and NSOs differ — including their tax treatment at grant, exercise, and sale — see Stock Options vs. RSUs vs. Actual Shares in Shareholder IQ.
What It Actually Costs to Exercise
Exercising stock options after leaving has two costs: the exercise cost and the tax.
Exercise cost: Strike price × number of vested options. If your strike price is $1.50 and you have 20,000 vested options, you write a check for $30,000. That's real cash, out of pocket, right now, to receive shares in a private company you can't immediately sell.
Example
You have 20,000 vested NSOs with a $1.50 strike price. The company's current 409A valuation implies a common share FMV of $12. Exercise cost: $1.50 × 20,000 = $30,000. The spread: $12 − $1.50 = $10.50 per share. Ordinary income added to your tax return: $10.50 × 20,000 = $210,000. At a 35% combined marginal rate, that's roughly $73,500 in taxes due this year — in addition to the $30,000 exercise cost — before you've sold a single share.
The critical issue: the tax is due the year you exercise. The shares remain illiquid — you can't sell them to fund the tax bill without finding a buyer for private shares through a secondary transaction, which takes time and depends on company approval and buyer availability.
Key concept
Exercising options doesn't mean you get cash. It means you convert a right-to-buy into shares — private, illiquid shares. You've spent real money to own something that may take years to become liquid. Whether that trade-off is worth it depends on the company's prospects, the size of the potential gain, and your personal financial position.
This is not tax advice. Consult a qualified tax professional before you exercise stock options — particularly before exercising ISOs, where AMT exposure can be significant.
Extended Exercise Windows
Some companies — typically those that have thought carefully about employee equity fairness — extend the PTEP well beyond 90 days. Extended windows of 2, 5, or 10 years are available at a growing number of VC-backed companies. The logic: the standard 90-day window forces employees to make a rushed, high-stakes financial decision at exactly the moment they're transitioning jobs, often with limited cash. An extended window lets former employees wait until a liquidity event before deciding whether to exercise.
With a 10-year PTEP, you don't have to exercise immediately after leaving. You can wait until the company reaches a natural liquidity moment — an acquisition, an IPO, or a secondary market transaction — before deciding. This is qualitatively different from the standard 90-day window, where inaction means permanent forfeiture.
To find out what your company offers: read your option grant agreement. Look for a section titled "Post-Termination Exercise Period" or "Exercise After Termination." If it isn't clear, ask your equity plan administrator or HR — before you finalize your departure date.
If You Don't Exercise in Time
The options expire. Permanently. There's no grace period, no exception request, no way to reinstate them — they return to the company's option pool and you receive nothing.
This is how former startup employees "lose" their equity — not through any active decision, but through inaction past the deadline. An employee with 50,000 vested options at a $2 strike price, on a company where shares have a current FMV of $15, could walk away from $650,000 in potential unrealized gain simply by missing the PTEP. The options don't go dormant. They don't wait. They expire.
⚠️ Your employer won't remind you. The plan administrator won't send a warning notice when you're two weeks from the deadline. Calendar the expiration date on your last day, and treat it as a hard deadline — because it is.
Steps to Take Before Your Last Day
If you're planning to leave a startup — or just received notice — take these steps before your departure is finalized.
Step 1: Get your grant documents. Request your option grant agreement(s) from HR or your company's equity administration platform (Carta, Pulley, or similar). This document specifies your exercise price, number of options granted, vesting schedule, and post-termination exercise period.
Step 2: Know what you have vested. Determine exactly how many options are vested versus unvested as of your anticipated last day. If you're timing your departure, moving it by a few weeks may vest a meaningful additional tranche.
Step 3: Identify ISO vs. NSO. Your grant agreement will identify the type. If you have ISOs and your PTEP is set to 90 days (or longer), know that the 90-day ISO-to-NSO conversion is an IRS rule — it applies regardless of your plan's stated PTEP.
Step 4: Calculate the full exercise cost. Strike price × vested options = exercise cash required. For NSOs (and for ISOs held beyond 90 days), also estimate the tax on the spread. The combined number is what you need to make an informed decision.
Step 5: Get an independent value estimate for your shares. The exercise decision depends on whether the shares are worth more than your total out-of-pocket cost. The company's last-round valuation is not what your common shares are worth — preferred investors get paid first. Get a share-class-specific estimate before you decide.
Step 6: Mark your PTEP deadline. On your last day, record the exact calendar date when your PTEP expires. Set a reminder 30 days before that date. The countdown is already running.
Step 7: Consult a tax professional before you exercise. The exercise decision is irreversible and can produce a significant tax event in the current calendar year. For large positions, the difference between exercising in December versus January can be the difference of one tax year's worth of AMT or ordinary income exposure.
Before you decide whether to exercise
Start with a free price estimate for your shares.
Earlyasset prices your shares by share class using secondary market data. Knowing what your common shares are actually worth — not the last preferred-round valuation — is the first step in any exercise decision.
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Earlyasset, Inc. does not provide investment advice and is not a registered investment adviser. Pricing estimates are algorithmic and do not constitute an offer to buy or sell securities. All transactions respect the company's right of first refusal (ROFR) and any transfer restrictions in your equity agreements. Direct liquidity is provided by Earlyasset Capital, LLC, a separate entity from Earlyasset, Inc.
Tax disclaimer: This article is general educational content only and does not constitute tax, legal, or financial advice. Tax treatment of stock option exercises varies significantly based on equity type (ISO vs. NSO), holding period, state of residence, individual circumstances, and other factors. Consult a qualified CPA, tax attorney, or financial advisor before making any exercise or transaction decision. Earlyasset, Inc. is not a tax advisor and does not provide tax guidance.