NYC Startup Equity Guide 2026: ISOs, NSOs, 83(b), and New York Taxes

ISO vs NSO: The Fundamental Distinction

Stock options come in two primary types, each with very different tax treatment:

ISOs: The AMT Trap in New York

ISOs are often presented as the superior option type because they defer regular income tax until sale. However, the spread at exercise (fair market value minus exercise price) is an Alternative Minimum Tax (AMT) preference item. Exercising a large ISO position in a single year can trigger significant federal AMT liability — and New York State has its own minimum tax calculation that can independently generate additional liability.

For NYC-based employees exercising ISOs on a startup that has appreciated significantly, the federal and New York AMT combined can create a tax bill on "paper gains" — you owe taxes before you can sell the stock. The 2026 federal AMT exemption is $137,000 (single) / $220,800 (married), phasing out above $1,220,700 / $1,956,450. Planning ISO exercises to stay within AMT exemption limits is critical.

NSOs: Cleaner, But Taxed Hard at Exercise

Non-Qualified Stock Options are taxed as ordinary income on the spread (FMV minus exercise price) at the time of exercise. For an NYC employee in the top combined tax bracket:

• Federal: up to 37%
• NY State: up to 10.9%
• NYC local: up to 3.876%
• FICA: 1.45% Medicare (no cap; 0.9% additional above $200K)
• Combined marginal rate on NSO exercise spread: ~52–54%

This is a sobering number. On an NSO with a $500,000 spread, a top-bracket NYC employee could owe $260,000–$270,000 in combined taxes — requiring either cash to pay or selling shares immediately.

The 83(b) Election: The Most Important 30-Day Deadline in Startup Tax

Section 83(b) of the Internal Revenue Code allows recipients of restricted property (including restricted stock, but not options themselves) to elect to be taxed on the current fair market value at grant rather than waiting until vesting. For early-stage startup founders who receive restricted stock:

• At founding: Stock may be worth $0.0001/share (par value). Filing an 83(b) means you pay taxes on essentially zero income.
• Without 83(b): As the stock vests and the company grows, you'd owe ordinary income tax on the FMV at each vesting date — potentially millions in ordinary income tax on shares you may not be able to sell.
• Deadline: Must be filed with the IRS within 30 days of the grant date. No exceptions.
• NY State: New York also requires a copy of the 83(b) election to be attached to your NY State tax return for the year of the election.

Vesting: Standard Terms and Negotiation

NYC startup equity typically follows Silicon Valley convention:

• Standard vesting: 4-year vest with 1-year cliff (25% vests after one year; remainder vests monthly or quarterly over the following 36 months)
• Acceleration: Some grants include single-trigger acceleration (vesting accelerates on acquisition) or double-trigger (requires both acquisition and termination)
• Post-termination exercise window: Standard is 90 days after leaving; some companies offer 5-year or 10-year windows. A shorter window forces employees to exercise (and pay taxes) or forfeit options.

409A Valuations: What They Mean for Your Options

A 409A valuation is an independent third-party appraisal of a private company's common stock FMV. Companies must obtain a 409A before granting stock options to establish a defensible exercise price equal to FMV. Key points:

• 409A FMV is typically significantly lower than the preferred share price investors pay (due to liquidation preferences, lack of control, illiquidity discount)
• A freshly completed Series A at a $50M valuation does not mean your common stock options are worth the implied $50M / shares outstanding — the 409A may value common stock at 30–50% of the preferred price
• Options must be granted at or above the 409A FMV to avoid Section 409A penalties
• 409A valuations must be refreshed at least every 12 months or upon material events (new funding round, acquisition discussions)

New York's Source Income Rules: The Hidden Tax on Moving

New York State has some of the most aggressive source-income rules in the country for stock options. If you worked in New York while options were granted and vesting, New York may tax a portion of the gains even after you move to a no-income-tax state like Florida or Texas. The general allocation method:

• NSOs: NY taxes the portion of the ordinary income spread at exercise allocable to NY workdays during the grant-to-exercise period
• ISOs: NY's allocation is generally based on grant-to-vest period for purposes of NY's own calculations
• RSUs: NY taxes the portion of vesting income allocable to NY workdays during grant-to-vest

This "clawback" effect means that moving to Florida before your options vest or are exercised will not fully eliminate your New York tax obligation if those options were earned while you were a NY resident. The longer you worked in New York relative to the total grant/vest period, the larger New York's claim.

Liquidation Preferences: Why Your Options May Be Worth Less Than You Think

Startup equity is often presented as a potential windfall, but liquidation preferences held by venture investors can dramatically reduce — or eliminate — the value of common stock options in acquisition scenarios below the most optimistic valuations. Key concepts:

• 1x non-participating preferred: Investors get their money back before common shareholders in a sale. At low acquisition prices, this may leave common shareholders with little.
• Participating preferred: Investors get their preference AND a pro-rata share of remaining proceeds — doubly dilutive to common
• Multiple liquidation preferences (2x, 3x): Investors get 2–3x their investment before common shareholders see proceeds. Common in down rounds or venture debt scenarios.

Before accepting a startup offer, ask for the cap table structure, total liquidation preferences outstanding, and a modeled acquisition scenario at 1x, 2x, and 5x current valuation to understand what your options would actually be worth.