Do I Owe Taxes If My Startup Stock Is Illiquid?
Illiquid stock doesn't defer tax. RSU vests, NSO exercises, and ISO AMT all create bills before you can sell. Here's when tax is due and how people fund it.
Private company equity creates a painful gap: the IRS taxes you when income is recognized — at RSU vest, NSO exercise, or ISO exercise for AMT — but you often can't sell shares to pay the bill. Liquidity might be years away.
The answer to 'do I owe tax?' is almost always yes, even if your shares are locked, subject to a board-approved transfer restriction, or worth nothing on a secondary market. Illiquidity affects how you pay, not whether you owe.
Planning for equity tax without a sale is one of the most common reasons startup employees keep cash reserves, exercise early when valuations are low, or pass on exercising options they can't afford to tax.
When tax is due without a sale
RSU vest (public or private): FMV taxed as wages on vest date. Private companies use 409A valuations to set FMV. You receive shares you cannot sell — tax is still due via withholding or estimated payments.
NSO exercise: Spread is ordinary income at exercise, regardless of whether a buyer exists for your shares.
ISO exercise: AMT on spread at exercise. No sale required to trigger Form 6251 liability.
409A valuations and FMV
Private companies must obtain 409A valuations to set option strike prices and FMV for tax events. After a funding round, 409A typically steps up — increasing spread on future exercises and RSU vest values.
You can't elect a lower FMV because you'd prefer it. The company's board-approved valuation controls for tax until a liquidity event reprices the market.
If you disagree with a 409A spike, your remedy is administrative (company process), not filing at a self-assessed lower value.
Funding the tax bill
Cash savings: Many advisors suggest setting aside 30–45% of expected equity income for federal, state, and FICA — higher in California.
Sell-to-cover (RSUs at public companies): Automatic partial sale at vest. Private companies rarely offer this.
Net exercise: Surrender shares back to the company to cover strike and sometimes taxes. You keep fewer shares but need less cash upfront.
Secondary sales and tender offers: When permitted, selling a portion on a secondary market can fund tax — watch company ROFR and insider trading policies.
Section 83(b) for restricted stock (not RSUs)
If you receive restricted stock (actual shares, not RSUs) early, filing an 83(b) election within 30 days taxes you on today's FMV instead of future vest FMV. Useful when FMV is pennies at seed stage.
RSUs don't qualify for 83(b) — there's nothing to elect until vest. Don't confuse RSUs with restricted stock grants.
83(b) is irreversible. If the company fails, you paid tax on stock that became worthless — the risk is real at early stage.
When walking away makes sense
If spread tax on NSO exercise exceeds what you'd pay for comparable exposure, exercising may be irrational. Letting options expire avoids tax but forfeits upside.
Early exercise of ISOs when FMV ≈ strike minimizes AMT. Waiting until the company is worth $500M before your first exercise can make AMT unbearable.
Bankruptcy or shutdown: worthless stock may generate a capital loss in the year you dispose of it, but ordinary income tax paid at vest or exercise generally isn't refundable — another reason to size exercises carefully.
Key takeaways
- Illiquid stock is still taxable at vest (RSU), exercise (NSO), or for AMT (ISO).
- 409A sets FMV for private company tax events — you can't pick your own value.
- Budget cash for tax independent of whether you can sell shares yet.
- Early exercise and 83(b) can reduce future tax when FMV is still low — with real downside risk.
This guide is for general education only and is not tax, legal, or accounting advice. Rules change, and your facts matter. Talk to a qualified professional before filing or making equity decisions.
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