Two deadlines sit inside every option grant, and neither one is mentioned in the excited conversation about equity that happens during hiring. The first decides whether you get anything at all. The second decides, potentially years later, whether you have to pay real cash for stock you may never be able to sell.
This is general information about how vesting cliffs and exercise windows typically work, not financial or tax advice, and it's not a substitute for reading your own plan document. Exercise deadlines, AMT exposure, and what happens to unexercised options at departure are all governed by the specific terms of your own grant and your own country's tax rules, which this post has not seen. For what decisions do vesting cliffs and exercise windows actually force framed around revenue rather than architecture, is the better starting point. For what decisions do vesting cliffs and exercise windows actually force framed around revenue rather than architecture, the XenGrowth practice is the better starting point.
The cliff: a wall, not a slope
The standard structure at most venture-backed companies is a one-year cliff followed by monthly or quarterly vesting through year four. "Cliff" is the right word, not a metaphor stretched thin: for the entire first year, the vested amount is exactly zero. It does not creep up gradually and then accelerate — it sits at nothing until the one-year mark, at which point roughly a quarter of the total grant vests all at once, and the remaining three-quarters then vest in smaller regular increments over the following three years. Leave on day 364 and the entire grant, all four years of it, is forfeited in full. Leave on day 366 and only the first year's quarter has vested — the other three-quarters are still unvested and still forfeited on departure. There is no partial credit for the eleven months worked before a cliff, under a standard schedule.
This shapes real decisions in ways companies rarely have to say out loud. An employee weighing an offer elsewhere at month ten of their first year is, whether they frame it this way or not, weighing that new opportunity against the entire value of their current unvested grant — not a fraction of it. The math changes completely a few weeks later, once the cliff has passed.
Time since start | Standard 1yr cliff / 4yr vest: amount vested | What departure means |
|---|---|---|
6 months | 0% | Entire grant forfeited on departure |
11 months | 0% | Entire grant still forfeited — one month early |
13 months (just past cliff) | ~25% | That quarter is vested and yours; the rest is forfeited |
30 months | ~62.5% | That portion vested; remainder forfeited |
48+ months | 100% | Fully vested; departure doesn't forfeit anything — but the exercise window still starts |
Fully vested is not the same as fully yours
This is the part that catches people who cleared the cliff and assumed the hard part was over. Vesting only determines whether you're entitled to exercise an option — it doesn't hand you the shares. For a stock option (as opposed to an RSU, which converts to actual shares at vesting with no purchase step), you still have to exercise: pay the strike price, in cash, to actually own the stock. And once you leave the company, a second, independent clock starts on how long you're allowed to do that. That's the post-termination exercise window, and for an incentive stock option in the US it is classically 90 days — a figure that comes directly from the requirements for ISO tax treatment under the tax code, not an arbitrary company policy. Miss it, and the option doesn't necessarily vanish outright, but per IRS Topic No. 427, the favorable ISO treatment specifically is what's at stake; many plans then allow the same option to be exercised as a nonqualified option instead, while others simply let it expire on the deadline stated in the option agreement. Which one applies to you is a plan-document question, not a general rule. covers the the operations side of this side of this. The XenGrowth resource library covers the the operations side of this side of this.
The bind: pay now for stock you may never sell
Put the two pieces together and the shape of the problem is clear. You've left the company, or are about to. You have vested, unexercised options. The company is private, so there's no market to sell into even if you wanted to cash out immediately. And a countdown — often 90 days — is running on your right to buy those shares at all. The decision is genuinely: pay cash now, out of pocket, for stock in a company you no longer work at and that may or may not ever be sellable at any price, or let the option lapse and lose it entirely. There is no third option that avoids both costs, and a short window gives you very little time to gather the information that would make this an informed decision rather than a forced guess.
A 90-day exercise window doesn't ask whether you can afford to buy stock in a company you no longer work for. It just starts counting.
The AMT makes the bind worse before it gets better
If the option is an ISO and the strike price is well below the current fair market value, exercising doesn't just cost the strike price in cash. It can also trigger the alternative minimum tax. Per the instructions for IRS Form 6251, the spread between fair market value and exercise price at the time of exercise gets added to alternative minimum taxable income — using the exact figures the company reports on Form 3921 — computed under a parallel tax system alongside your regular return. That's a real tax bill, potentially a large one, on a stock you cannot sell yet, arriving with no cash from a sale to cover it. The one meaningful exception the instructions carve out: no AMT adjustment is required if the stock is sold in the same calendar year it's exercised, since a same-year sale collapses the whole thing into one ordinary transaction instead.
This is exactly why the decision to exercise after leaving a company is not purely about believing in the company's future. Even a genuine belief that the shares will eventually be worth far more than the strike price doesn't make an AMT bill due next April any less real, and a private company offering no way to sell shares to cover that bill is a specific, concrete cash-flow problem, not an abstract risk. approaches this from the AI agents and marketing automation side. XenGrowth on AI agents and marketing automation approaches this from the AI agents and marketing automation side.
Some companies have moved the wall
The 90-day window is a US tax-code artifact of ISO treatment specifically, not a law of nature for all options everywhere, and a small but growing number of companies have chosen to change it. Coinbase announced an extension of its post-termination exercise window from the standard 90 days to as long as seven years for employees with at least two years of tenure, framing it explicitly as removing the pressure to pay cash immediately upon leaving or lose the equity. Pinterest made a comparable move, also to a seven-year window for tenured employees. In both cases, the mechanism required is the same: since ISO tax treatment is tied by law to a short exercise tail after termination, extending the window well beyond that means converting the affected options to nonqualified stock options — trading the ISO's tax advantage away in exchange for time.
Exercise window | Who it typically applies to | Trade-off involved |
|---|---|---|
~90 days (standard ISO) | Most employees at most companies, by default | Preserves ISO tax treatment, but forces a fast pay-or-lose decision at departure |
Several months to a year (some companies) | A smaller number of companies with modestly extended plans | More breathing room, still typically tied to remaining within ISO rules or accepting NSO conversion |
7 years (Coinbase, Pinterest) | Employees with at least ~2 years of tenure at those specific companies | Options convert from ISOs to NSOs to legally support the longer tail, trading ISO tax treatment for time |
Full original option term (a handful of companies) | Rare; some companies extend to the option's full 10-year term | Maximum flexibility, same ISO-to-NSO conversion trade-off applies |
None of this is a reason to assume your own company has, or hasn't, adopted an extended window — the only reliable way to know is to read your specific plan document or ask whoever administers equity at your company directly. A general awareness that extended windows exist is useful mainly so you know the standard 90-day figure is a common default, not a fixed rule you're powerless to ask about.
What actually changes once you've left
It's worth being specific about what departure changes and what it doesn't. Vesting itself normally stops the day you leave — unvested shares don't continue accruing after your last day, regardless of how the exercise window is structured. What the exercise window governs is only the shares that had already vested by that point: the ones you'd earned the right to buy, but hadn't yet bought. A generous exercise window doesn't restore anything that was still unvested when you left; it only extends how long you have to act on what you'd already earned. goes further into AI search, GEO and discovery. XenGrowth on AI search, GEO and discovery goes further into AI search, GEO and discovery.
This distinction matters because the two clocks in this post — the vesting cliff and schedule on one side, the post-termination exercise window on the other — are answering two different questions entirely. The first asks how much of the grant you actually earned by staying as long as you did. The second asks how long you have to convert what you earned into actual owned stock. Confusing the two is a common and costly mistake: a fully vested grant with a short exercise window is not a safe position just because nothing is at risk of being unvested anymore.
Find your actual plan document and get your specific post-termination exercise window in writing — don't assume 90 days applies without checking
If you're near a cliff and considering leaving, know exactly how many vested shares you'd have on each side of that date before deciding on timing
If you're facing an exercise deadline, get a real number for the exercise cost and any AMT exposure from your own grant's figures, not a rule of thumb
Check whether your company offers an extended exercise window — it isn't standard, but it isn't rare anymore either, and it changes the entire calculation if it applies to you
Talk to a qualified tax advisor before exercising anything meaningful — the AMT interacts with the rest of your tax return in ways a general post like this one cannot model for your specific situation
None of this is financial or tax advice, and it hasn't seen your plan document, your grant's numbers, or your tax situation — all of which change the actual answer for you specifically. What it should leave you with is the shape of the two deadlines: one that decides whether you get anything, and one that decides, on a much shorter fuse, what it costs you to keep it. is a useful adjacent read on the operating side of the growing companies that grant this kind of equity in the first place.
Further reading from XenGrowth
Where this work meets go-to-market
Building or managing equity programs from inside a commercial team? cover the revenue operations side of the same growing companies that write these grants.
Further reading from XenGrowth
Where this work meets go-to-market
The operational playbooks that sit alongside what decisions do vesting cliffs and exercise windows actually force live with .
Further reading from XenGrowth
The XenGrowth resource library — what you'll learn: how the commercial side of this work is run, across search, automation and revenue operations.
XenGrowth on AI agents and marketing automation — what you'll learn: how the teams who own AI agents and marketing automation plan and measure it.
XenGrowth on AI search, GEO and discovery — what you'll learn: how the teams who own AI search, GEO and discovery plan and measure it.
Where this work meets go-to-market
The operational playbooks that sit alongside what decisions do vesting cliffs and exercise windows actually force live with XenGrowth.
A handful of questions about the situation you're actually facing with a vested or partially vested grant. This is not financial or tax advice — it hasn't seen your grant documents, your plan's actual rules, your cash position, or your tax situation, all of which change the real answer.
