Exercising Stock Options in 2026: $6,000 to Buy the Shares, $6,720 to the IRS

Options get described as a reward, so the verb people attach to them is collect. The mechanics are the opposite. Exercising is a purchase: you send money to your employer, you receive shares, and depending on which kind of option you hold, a tax bill either arrives with the purchase or waits quietly until April.

Almost everyone meets those two bills in the wrong order. The strike price turns up first, usually in the week someone resigns and a 90-day clock starts. The tax turns up months later, when a preparer runs Form 6251 and finds a large gain on stock that still cannot be sold — by which point the year that would have let you split the exercise has closed. This describes the mechanics; it is not tax or legal advice, and every grant's terms differ.

One grant, two tax regimes

The most consequential line on a grant letter names the instrument. The same 3,000 options, the same $2 strike, the same $10 valuation produce two very different cash schedules.

The ISO column looks cheaper, and in the year you exercise it usually is. What it hides is that the ISO bill is uncertain, unwithheld, and arrives when you have no shares to sell to pay it. The NSO bill is larger but announces itself. Put your own strike price and latest 409A number into the stock option exercise cost calculator and both columns move together.

Two things sit outside the table. An NSO spread is wages, so payroll tax applies: Medicare at 1.45% and Social Security at 6.2% until your wages pass $184,500 in 2026, roughly another $1,800 on a $24,000 spread. And payroll withholds federal tax at the flat 22% supplemental rate — $5,280 here — against $7,680 of actual federal tax at a 32% bracket. That leaves $2,400 deferred to April before state tax, which is why checking which bracket the spread lands in matters more than the withholding line on the payslip.

The $6,720 is a ceiling, not a bill

That AMT figure is deliberately pessimistic: it is 28% of the spread, 28% being the top AMT rate, so it is the worst the spread can do rather than what you will owe. Three things pull the real number down.

The exemption first. The AMT starts from your regular income plus the ISO spread, then subtracts an exemption of roughly $90,000 for a single filer and $140,000 for joint filers in 2026 — a figure that phases out at higher incomes, with the threshold in the Form 6251 instructions. A spread small next to that exemption can produce nothing.

Then the rate: above the exemption, the first $244,500 is taxed at 26%, not 28%. A $24,000 spread never reaches the 28% band on its own.

Third, and most misunderstood: the AMT is not stacked on your normal tax. You compute both and pay the higher, so you hand over only the amount by which the tentative minimum tax exceeds your regular tax — and what you do pay becomes an AMT credit usable in later years, closer to a forced deposit than a cost.

None of that helps if you find out in April. The one lever that exists — splitting an exercise across two calendar years so neither year's spread clears the exemption — only works before 31 December.

The 90-day window is what forces the decision

Most people never choose to exercise. They are made to.

The standard post-termination window is 90 days from your last day. Miss it and vested options expire worthless, however much the stock is notionally worth. That is why a resignation turns into a cash problem: 3,000 options at a $2 strike need $6,000 immediately, and $14,880 if they are NSOs. Neither the number nor the deadline is negotiable, so work the figure out before you hand in notice rather than during the 90 days.

Some companies now offer extended windows of five to ten years, and a small industry of lenders will fund an exercise for a share of the upside. Both are worth knowing before you resign, because the window is a term of the plan rather than something HR can grant on the way out.

One grant-letter detail explains why many people hold both kinds of option at once: only the first $100,000 of options, counted at the strike price, that become exercisable in a single calendar year can be ISOs. Anything above that is treated as NSOs by law. At a $2 strike that line sits at 50,000 options a year, and accelerated vesting pushes people over it more often than they expect.

Early exercise, and the 30-day clock on the 83(b) election

If your plan permits early exercise, the arithmetic changes completely. Exercise while the fair market value still equals the strike price and the spread is zero: no wage tax on an NSO, nothing to add to Form 6251 for an ISO, and the capital gains clock starts at the earliest possible date.

The condition is the 83(b) election, filed with the IRS within 30 days of exercising unvested shares. Miss it and the tax is measured tranche by tranche as each one vests, at whatever the company is worth then. Thirty calendar days, no extensions, no relief for filing late.

The cost is blunt: cash for shares in a company that may be worth nothing, and most are. Sell ISO shares at least a year after exercise and two years after grant and the whole gain is taxed at 15% or 20% rather than as ordinary income — if there is a gain, and if a buyer exists.

Buying something you cannot sell

The tax code treats the 409A valuation as the value of your shares. Your bank account does not. A 409A price is an appraisal for setting strike prices, not a price anyone will pay you, and in most private companies you are contractually barred from selling without board consent.

So the ISO exercise above sends $6,000 out of the door, may add an April bill on a $24,000 gain, and leaves you holding an asset with no market. If the company fails, the tax is not refunded; the loss becomes a capital loss, whose deduction against ordinary income is capped annually under IRS Publication 550. If it succeeds, liquidation preferences are paid before common stock, so the eventual take-home from a sale is usually well below your percentage of the headline price.

That is the real question, and it is not a tax one. Running the same grant at several valuations shows how fast the exposure grows against the cash you put up.

FAQ

If I hold ISOs, why does anyone talk about tax at exercise at all?

Because "no tax" describes only the regular tax system. Exercising an ISO triggers no ordinary income and nothing is withheld, but the spread is an adjustment on Form 6251 and enters the parallel AMT calculation. On a $24,000 spread the exposure tops out at $6,720, payable in cash in April whether or not you can sell a share. The spread never reaches Form 6251 in one case only: exercising and selling in the same calendar year, which disqualifies the ISO treatment and taxes the spread as ordinary income.

My employer withheld tax on my NSO exercise. Am I settled up?

Probably not. Payroll withholds on a supplemental item like an option spread at a flat 22%, rising to 37% only above $1,000,000 in a year. On the $24,000 spread that is $5,280 withheld against $7,680 of federal tax at a 32% bracket, leaving $2,400 at filing plus whatever your state adds. Set the difference aside the same week you exercise.

I left a job three months ago and did nothing. Are my options gone?

If your plan carried the standard 90-day post-termination window, yes — vested options not exercised in that period expire, and the value is not recoverable. Check the grant letter rather than assuming, because extended windows of five to ten years exist and a few plans measure from a different date. Unvested options were forfeited on your last day in almost all plans regardless.

Can I exercise part of my grant instead of all of it?

Almost always, and it is the main lever a holder actually has. Cash and spread both scale linearly, so exercising 1,000 of those 3,000 options costs $2,000 and creates an $8,000 spread rather than $24,000. Splitting across two calendar years keeps each year's spread small relative to the AMT exemption — and the choice disappears once 31 December passes.

Sources

• IRS Topic No. 427, Stock Options — https://www.irs.gov/taxtopics/tc427
• IRS, About Form 6251, Alternative Minimum Tax — Individuals, and its instructions, which carry the 2026 exemption and phase-out thresholds — https://www.irs.gov/forms-pubs/about-form-6251
• IRS Publication 550, Investment Income and Expenses, on capital losses
• Internal Revenue Code §422 (the $100,000 annual ISO limitation; the one- and two-year holding periods) and §83(b) (the 30-day election on unvested property)
• 2026 federal brackets and the $184,500 Social Security wage base, per IRS Rev. Proc. 2025-32 and the Social Security Administration

General information about how these rules work, not tax, legal or investment advice. Option terms, exercise windows and plan rules vary from one grant to the next, and the figures above are worked arithmetic for one example rather than a statement about your grant.