Leaving Carta? Plan your 90-day ISO window
Calculator · free · no signup · pre-IPOCarta is pre-IPO. Left with vested ISOs? Model the 90-day exercise-or-forfeit decision and its AMT cost at any valuation: current 409A or an expected exit price.
Beta · invite-only · AlphaLatitude Inc. · Free Tools
Your grant
Seeded from secondary-market data, as of Jun 9, 2026
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: $77,656 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.
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.
| 1 | 10,000 | |||
| 2 | 0 | |||
| 3 | 0 |
Federal AMT credit
Earned
$16,382
Recovered
$16,382
Remaining
$0
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 →About Carta
Carta is a privately held Fintech company, incorporated in Delaware and headquartered in San Francisco, CA.
Last reported secondary-market price: $16.77 per share (as of 2026-06-09). Your own 409A may differ.
Cap table software.
Equity grants at Carta typically include incentive stock options (ISOs) and non-qualified stock options (NSOs).
eShares, Inc., doing business as Carta, Inc., is a San Francisco, California-based technology company that specializes in capitalization table management and valuation software. The company digitizes paper stock certificates along with stock options, warrants, and derivatives to allow companies, investors, and employees to manage their equity and track company ownership. The company also operated CartaX, a private stock exchange, which was shuttered in 2024.
Source: Wikipedia (CC BY-SA 4.0)
Henry Ward and Manu Kumar founded Carta, originally eShares, in 2012 to digitize paper stock certificates and replace spreadsheet-based cap tables with auditable, legally compliant software. Companies use Carta to issue equity, model dilution, run 409A valuations, and manage employee option exercises. The platform expanded to serve venture funds with LP portfolio management tools. Carta raised $500 million in a Series G led by Silver Lake in August 2021 at a $7.4 billion valuation, its last disclosed primary round, and reached $442 million in annual recurring revenue in 2024.
Sources: en.wikipedia.org · techcrunch.com
Equity comp at Carta
- Carta issues single-trigger RSUs (awards where shares vest and settle immediately on each vesting date, with no separate IPO or acquisition trigger required) to its own employees, providing liquidity through quarterly windows on its own private secondary platform, Carta Liquidity. At each window, Carta withholds shares equal to the employee tax liability and remits taxes directly, so employees receive net shares with no out-of-pocket tax obligation at vest. Current employees may sell up to 20% of vested holdings per window. This structure makes a second liquidity-event trigger unnecessary: liquidity occurs on a schedule rather than only upon an IPO or sale.
- Early exercise is not allowed: you have to wait for shares to vest before you can buy them.
Sources: carta.com · carta.com · henrysward.medium.com
Researched 2026-05-10.
OptionsAhoy is an independent tool and is not affiliated with, endorsed by, or sponsored by Carta.
If you are leaving Carta with vested incentive stock options (ISOs), most stock plans give you 90 days from departure to exercise or forfeit them. The calculator works at any valuation: enter your strike and the current 409A fair market value (FMV) or an expected exit price. It computes your window deadline, the alternative minimum tax (AMT) cost of exercising in full, and the partial-exercise share count that maximizes expected after-tax value.
Example: leaving Carta with 5,000 vested ISOs at a $5.03 strike, with the last reported price at $16.77, exercising all of them inside the 90-day window puts a $58,700 bargain element into one tax year. Above the 2026 federal AMT exemption ($88,100 single, $137,000 married joint), the 28% AMT rate adds roughly $16,436 on top of regular tax before any state AMT (CA, CO, CT, MN). Exercising fewer shares lowers that bill at the cost of forfeiting the rest; the calculator above finds the count that maximizes expected after-tax value for your exact figures.
All Carta tools → · Use the generic Post-Termination ISO Exercise Calculator for any company.
Carta equity questions
- I left Carta. How long do I have to exercise my ISOs?
- Most stock plans give you 90 days from your departure date to exercise vested incentive stock options (ISOs); unexercised options are forfeited when the window closes. Tax law is slightly wider: ISO treatment requires you to have been an employee within 3 months of exercise (Internal Revenue Code Section 422(a)(2)), so options exercised under an employer-extended window are taxed as non-qualified stock options (NSOs). Check your grant agreement for Carta's exact terms. The calculator above computes your deadline from your departure date, the alternative minimum tax (AMT) cost of exercising, and the share count that maximizes after-tax value.
- Does Carta grant ISOs, NSOs, or RSUs?
- Equity compensation at Carta typically takes the form of incentive stock options (ISOs) and non-qualified stock options (NSOs). Incentive stock options can trigger the alternative minimum tax (AMT) when you exercise.
- Does Carta allow early exercise of stock options?
- No. Carta requires options to vest before you can exercise them, so the holding-period clock for long-term capital-gains treatment starts as each tranche vests and you exercise it.
- Are Carta shares eligible for QSBS?
- They might be. Qualified small business stock (QSBS) under Internal Revenue Code Section 1202 can exclude federal tax on much of the gain when shares were acquired at original issuance from a C-corporation while its gross assets were under $50 million, and held at least five years. Whether your Carta shares qualify turns on when you acquired them and the company's asset size at that time.
One piece of the puzzle.
OptionsAhoy plans your Carta equity alongside hedging, vesting, and de-concentration, across bullish, neutral, and bearish market scenarios. Free during beta.