Startup Equity Tax Timeline: Every Milestone From Grant to Exit
Equity compensation generates a tax event at almost every stage of a startup's life, and each one runs on its own clock. Miss the 30-day window on an 83(b) election, exercise an ISO at the wrong moment, or sell QSBS one month before the five-year mark, and the mistake is frequently permanent. This page lays out the full sequence in one place: what happens at grant, what happens at vesting, what happens at exercise, what happens around an IPO, and what recurs every quarter for the life of the position.
This is a map, not a return preparation tool. It is built to help you recognize which stage you are at and which section of the Internal Revenue Code governs it, so you know what question to bring to a qualified tax advisor and when to bring it. Every date and threshold below is general, current-law information as of the 2025 tax year. Nothing on this page is personalized tax, legal, or financial advice, and none of it accounts for your specific facts. Download the PDF version below to keep next to your cap table.
The Timeline
Six phases, thirteen events. Gold markers are the ones with a hard deadline or an irreversible tax consequence. Navy markers are administrative or recurring.
Grant Date & the 83(b) Election Window
Restricted stock (not RSUs) starts a strict 30-day clock under IRC §83(b). Filing an 83(b) election locks in ordinary income tax on the value at grant, generally low or zero for early-stage founders, and starts capital-gains treatment on future appreciation. The window does not extend for weekends, holidays, or company delay. Missing it is not curable.
Vesting Begins: Cliff & Vest Schedule
A typical schedule runs a one-year cliff followed by monthly or quarterly vesting over four years. RSUs generally recognize ordinary income at each vest date (the value of the shares that vest). Options (ISOs and NSOs) become exercisable as they vest, but exercise is a separate, elective event with its own tax consequence.
ISO Exercise: the AMT Trigger
Incentive stock options are governed by IRC §421–§424. Exercising an ISO generally creates no regular-tax income at exercise, but the spread between strike price and fair market value is an alternative minimum tax preference item under IRC §55–§59. A large exercise in a single calendar year can trigger substantial AMT liability even though no shares were sold.
NSO Exercise: Ordinary Income
Non-qualified stock options do not receive ISO treatment. The spread at exercise is taxed as ordinary income (and subject to payroll withholding) in the year of exercise, generally reported on Form W-2. There is no AMT preference item for NSOs because the income is already ordinary at exercise.
QSBS 5-Year Clock Starts
If the company is a qualifying C-corporation, stock acquired at original issuance may be Qualified Small Business Stock under IRC §1202(a)(1). The five-year holding clock generally starts at exercise for options, not at grant. Exercising late (for example, after an acquisition is announced) restarts this clock at the worst possible time.
Secondary Sales & Tender Offers
A tender offer or secondary sale is a taxable sale. If QSBS shares have not yet crossed the five-year mark, participating triggers gain with no Section 1202 exclusion available. This decision should generally be modeled against the QSBS clock before shares are tendered.
IPO / Direct Listing: RSU Dual-Trigger Vests
Many pre-IPO RSU grants use a dual-trigger structure: time-based vesting plus a liquidity event condition. At IPO, any tranches that satisfied the time condition generally vest and recognize ordinary income all at once, which can create a large single-year income spike and a mismatch between tax withheld and tax owed.
Lockup Expiry
The underwriter-imposed lockup period generally prevents insiders from selling for a set number of days after the offering. The first sale window after lockup expiry is often when employees and founders realize their first liquidity, and the first point at which capital-gains planning around cost basis and holding period becomes actionable.
10b5-1 Plan Adoption
Executives and insiders subject to trading restrictions often adopt a Rule 10b5-1 trading plan to schedule sales in advance and reduce insider-trading exposure. Plan timing interacts with holding-period math (short-term versus long-term capital gains) and should generally be set up with a securities attorney alongside your tax advisor.
QSBS 5-Year Mark: Exclusion Available
Once the five-year holding period under IRC §1202 is satisfied and all qualification gates were met at issuance, a sale can qualify for a 100% federal exclusion on gain up to the greater of $10 million (or $15 million for stock acquired after July 4, 2025, per OBBBA) or ten times adjusted basis, per taxpayer, per issuing corporation. Selling one day early forfeits the entire exclusion on that lot; see our full QSBS / Section 1202 timeline and planning guide.
ESPP Qualifying Disposition
Under IRC §423, an Employee Stock Purchase Plan sale is a "qualifying disposition" only if held more than two years from the offering (grant) date and more than one year from the purchase date. Meeting both generally shifts most of the gain from ordinary income to capital gain. Selling before either date is a disqualifying disposition (see below).
Disqualifying Disposition (ISO or ESPP)
Selling ISO shares within one year of exercise or two years of grant, or selling ESPP shares before the §423 holding periods above, is a disqualifying disposition. The bargain element generally becomes ordinary income in the year of sale rather than capital gain, and for ISOs it can also affect the AMT credit calculation from the exercise year.
Quarterly Estimated Taxes & the 110% Safe Harbor
NSO exercise income, RSU vest income above withholding, and QSBS or capital-gain sales generally are not fully covered by employer withholding. Form 1040-ES estimated payments are usually required. For taxpayers with prior-year AGI over $150,000, the safe harbor under IRC §6654(d)(1)(B) requires paying in the lesser of 90% of the current year's tax or 110% of the prior year's tax to avoid an underpayment penalty. California generally does not conform its own supplemental-withholding rate (a flat rate on bonus-type income) to actual marginal liability, which routinely leaves a state gap that estimated payments must close.
This timeline is general educational content and does not reflect every fact pattern. Equity plan terms vary by company, and state tax treatment varies by residency. Consult a qualified tax advisor before making any election, exercise, or sale decision based on dates or thresholds shown here.
How Silicon Valley Tax Uses This Timeline
Cooper Hathaway and Alfonso Nuñez, Managing Partners at Silicon Valley Tax, use a version of this same sequence as the starting framework in every equity compensation engagement: confirm which phase a client's grants are in, map the relevant deadlines against the client's actual grant documents and vesting schedule, and flag any window (an 83(b), an ISO exercise, a QSBS clock) that is close to expiring before it becomes irreversible. For a deeper look at any single stage, see our dedicated pages on startup equity tax planning, RSU withholding, QSBS / Section 1202, and AMT planning.
FAQ: Startup Equity Tax Timeline
Is the 83(b) election deadline really 30 days with no exceptions?
Generally yes. The 30-day window under IRC §83(b) runs from the date of transfer (grant), and the IRS has historically applied it strictly with essentially no relief for late filing due to inadvertence. Because of how rigid this deadline is, most advisors recommend filing well before day 30, not on it. Confirm your specific filing mechanics with a qualified tax advisor immediately after a restricted stock grant.
Does the QSBS clock start at grant or at exercise?
For options (ISOs and NSOs), the clock under IRC §1202 generally starts at exercise, when shares are actually issued, not at the grant date. For restricted stock with a timely 83(b) election, the clock generally starts at grant. This distinction is one of the most commonly misunderstood points on this entire timeline.
Do I owe AMT even if I do not sell my ISO shares?
Potentially, yes. The AMT preference item under IRC §55–§59 is triggered by the exercise itself, based on the spread between the strike price and fair market value at exercise, regardless of whether the shares are later sold. This is a common surprise for employees exercising a large ISO grant at a private company where the shares cannot easily be sold to cover the resulting tax.
What happens if I miss the ESPP qualifying disposition window by a few days?
The IRC §423 holding periods (two years from offering, one year from purchase) are bright-line dates. Missing either by even one day generally converts the sale to a disqualifying disposition, shifting the bargain element from capital gain to ordinary income. There is no partial credit for holding 729 out of 730 days.
Why would I owe an underpayment penalty if my employer withheld taxes?
Employer withholding on RSU vests and NSO exercises is often calculated using flat statutory rates that do not match your actual marginal tax bracket, and it does not cover QSBS or other capital-gain sales at all. If your total withholding and estimated payments fall short of the safe harbor under IRC §6654(d)(1)(B), a penalty can apply even though tax was withheld on part of your income.
Talk to Us Before Your Next Vesting Event
This timeline is the map. The specific dates, elections, and thresholds that apply to your grants depend on your equity plan documents, your company's entity structure, and your own tax situation. Cooper Hathaway and Alfonso Nuñez work with Bay Area founders and employees across every phase shown above. Book a complimentary consultation or call us at (408) 383-9870 to walk through where your grants sit on this timeline.