Equity compensation is one of the most common reasons a tech employee or founder ends up with a surprising tax bill. The rules differ sharply depending on the instrument, and the most expensive mistakes come from assuming your employer's withholding has it covered. It usually does not.
RSUs: ordinary income, often under-withheld
Restricted stock units are taxed as ordinary income when they vest, on the full market value of the shares — it shows up on your W-2. The trap is withholding: employers typically withhold federal tax at the flat 22% supplemental rate (37% on amounts over $1 million). If your marginal rate is 32% or 37%, that leaves a gap you have to cover through estimated payments or at filing. After vesting, your basis equals the value taxed at vest; watch for brokerage 1099-Bs that report $0 basis and would otherwise tax you twice on the same shares.
ISOs: where the AMT lives
Incentive stock options are the subtle one. Exercising an ISO and holding the shares past year-end creates no regular tax — but the bargain element (market value minus strike) is a preference item for the Alternative Minimum Tax. Exercise a large block of appreciated ISOs and hold, and you can owe AMT on income you have not received in cash. Sell in the same calendar year (a disqualifying disposition) and the AMT issue disappears, but the gain becomes ordinary. Hold more than one year from exercise and two years from grant for a qualifying disposition taxed at long-term capital gains rates.
NSOs and ESPP, briefly
- NSOs are taxed as ordinary income on the bargain element at exercise, with withholding — simpler than ISOs, no AMT preference.
- ESPP discounts are taxed partly as ordinary income; whether your disposition is "qualifying" depends on holding periods that start at the offering and purchase dates.
- Early exercise / restricted stock can involve an 83(b) election, which must be filed within 30 days — a deadline with no second chances.
Liquidity events and state lines
An IPO or tender offer concentrates years of equity into one tax year, often at the top rate, sometimes alongside lockups that limit when you can sell. And if you changed states during the vesting period, more than one state may claim a slice of the income. These are exactly the moments where planning ahead of the event — not after — changes the outcome.
The bottom line: model the AMT before you exercise and hold ISOs, and set aside cash for the gap between 22% withholding and your real marginal rate on RSUs. Equity-comp planning is most valuable in the months before a vest or a liquidity event, while you still have choices.
This article is general information, not tax, legal, or accounting advice, and reading it does not create a CPA-client relationship. Tax rules change and depend on your specific facts — please consult a qualified professional about your situation before acting.