Leaving your company? Plan your 90-day ISO window

Calculator · free · no signup

Most stock plans give you 90 days after departure to exercise vested incentive stock options (ISOs) or forfeit them. See your deadline, the alternative minimum tax (AMT) cost of exercising everything at once, and the share count that maximizes your after-tax value.

Beta · invite-only · AlphaLatitude Inc. · Free Tools

Your grant

pre-IPO? leave blank — enter price + growth manually
3 yrs
10%
20%
5.0%

Tax inputs

Grant timeline

Recommended exercise quantity

Exercise all 10,000

With 10%/yr expected growth over the 3-yr hold, every share's expected after-tax gain exceeds its marginal AMT cost. Net value: $171,946 at horizon.

Net after-tax value vs. shares exercised

Each point is the expected after-tax NPV at your hold horizon if you exercise that many shares now and let the rest expire.

$0$43K$86K$129K$172K02,5005,0007,50010,000
Recommended (10,000)Full exercise (10,000)

Year-by-year tax breakdown

You pay the higher of Regular tax and Tentative AMT per jurisdiction, then subtract Credit recovered. The result is Net tax. Hover any number for the bracket-by-bracket breakdown.

110,000
20
30

Federal AMT credit

Earned

$134,654

Recovered

$29,764

Remaining

$104,890

The AMT credit only recovers in years where regular tax exceeds AMT — typically a year with no ISO exercise. It carries forward indefinitely (Form 8801) and applies in any future tax year where regular tax exceeds AMT.

Estimates only. Excludes disqualifying dispositions, NSOs, multi-state moves, and AMT preferences other than ISO bargain elements. Long-term capital gains tax assumes a qualifying disposition (ISO held ≥1 yr from exercise and ≥2 yr from grant); state LTCG follows ordinary brackets except where the state grants preferential treatment (HI, ND, SC, WI, AR, NM) or has a dedicated LTCG-only tax (WA). Assumes you are within the $100K ISO limit (any portion of an annual ISO grant whose FMV at grant exceeds $100K is treated as NSO from the start, §422(d)). State AMT figures are 2025 (next-year values published in late 2026). Not financial advice.

QSBS note. If your shares qualify (typically pre-IPO C-corp grants held 5+ years), a federal rule lets you exclude up to $10M of gain on a future sale from federal tax. That single rule shifts exercise-timing math more than AMT does. (This is §1202 “qualified small-business stock”.) Modeled in beta, not here.

You solved the exercise window. The beta plans what comes after it: the new shares, your remaining equity, hedges, and taxes in one multi-year plan.

Request beta access →

What this calculates

  • Your exercise window deadline: departure date plus 90 days, with a day count until it closes.
  • Why multi-year AMT spreading is off the table: the window forces the whole exercise decision into year one.
  • The Alternative Minimum Tax (AMT) cost of exercising your vested ISOs at once: AMT on the bargain element (fair market value minus strike), with state add-ons for CA, CO, CT, and MN.
  • The partial-exercise share count that maximizes expected after-tax value at your hold horizon, traded against forfeiting the rest.
  • Year-by-year tax after the exercise, including AMT credit recovery in later years.

Models your plan's standard 90-day window. ISOs exercised more than 3 months after departure lose ISO treatment under IRC §422(a)(2) and are taxed as NSOs; model an extended window with the NSO calculator. Doesn't replace your CPA.

Methodology

Optimization. For a departed equity holder inside the 90-day post-termination window, the schedule decision collapses to one dimension: how many vested ISOs to exercise before the deadline (the rest are forfeited). The optimizer scans the exercise-count range from zero to your full vested count (grid scan with refinement around the best candidate), scoring each count against federal and state AMT in the exercise year and expected after-tax value at your hold horizon. Returns the count that maximizes expected after-tax value, alongside the full-exercise comparison. The search is deterministic: the same inputs return the same answer, so the recommendation is verifiable.

Tax-code coverage. Full federal code (ordinary brackets, long-term capital gains, AMT with credit recovery, FICA, Net Investment Income Tax) plus all 50 states and DC for state ordinary brackets and LTCG treatment. State AMT modeled for CA, CO, CT, MN. Brackets reflect IRS Rev. Proc. 2025-32 and the One Big Beautiful Bill Act (OBBBA) provisions for tax year 2026. Validated against 870+ unit tests covering bracket math, AMT credit recovery, state conformity, and the optimizer's search path.

Why use an optimizer rather than asking an LLM to do the math: a benchmark of five frontier large language models on the same multi-year ISO problem found that all 15 trials overshot the achievable after-tax outcome by 2x to 20x (HackerNoon write-up).

AI assistant integration

Use this from Claude, Cursor, or VS Code

Ask your agent:

“I left my company 3 weeks ago with 8,000 vested ISOs at $5 strike, FMV $40. How many should I exercise before my 90-day window closes?”

With the OptionsAhoy MCP installed, your agent calls amt_iso_optimize and returns the same after-tax answer this calculator computes.

Add to CursorAdd to VS CodeAll install options →
Find your company158 companies

You solved the window. The beta plans what comes after.

OptionsAhoy plans your full equity portfolio: the shares you just exercised, remaining NSOs, RSU vests, hedges, and sales, weighted by bullish, neutral, and bearish scenarios. Free during beta.

Request beta access