The 83(b) Election: The 30-Day Startup-Equity Decision You Can't Take Back

An 83(b) election tells the IRS to tax your restricted stock now, on its grant-date value, instead of at each vesting date. You must file within 30 days of the grant, a deadline the IRS does not extend. It can cut tax sharply on early-stage equity, but the tax you prepay is not refunded if the shares later fail.

Two things drive this whole decision. First, when the tax is measured. Second, what the shares are worth on that day. For a Sorrento Valley or Torrey Pines startup where the stock is worth almost nothing at grant, moving the tax to the grant date can be the difference between a rounding error and a bill at ordinary rates on every future vest. The catch is that the same move is irreversible, and it can cost you if the company never gets there. This walks through the mechanic, the clock, and the condition under which filing is the wrong call. For the fuller picture on equity at a life-science company, see our financial planning guide for San Diego biotech and life-science professionals.

What the 83(b) election actually changes

Restricted stock granted for services is normally taxed as it vests, on the value at each vesting date. Keep in mind what that means at a company whose value is climbing: each year a slice vests, and each slice is ordinary income measured at that year’s higher price. The stock got more valuable, so your tax bill did too, before you ever sold a share.

An 83(b) election flips the timing. You elect to be taxed at grant, on the grant-date value, and nothing more is due as the shares vest. The IRS describes the election on Form 15620 as choosing to include in your gross income now the excess of the restricted stock’s grant-date fair market value over anything you paid for it (IRS Form 15620, Section 83(b) Election, Rev. 4-2025). At an early-stage startup that excess is often tiny or near zero.

There is a second, quieter effect. The election starts your long-term capital gains holding clock at grant instead of at vesting. Long-term treatment requires holding more than one year (IRS, Topic no. 409, 2026), so starting the clock early can convert a later sale from ordinary income into long-term gain. That gap matters: the top 2026 ordinary rate is 37%, while the top long-term capital gains rate is 20% (IRS, Rev. Proc. 2025-32, tax year 2026), before the separate 3.8% net investment income tax that applies above $250,000 of modified AGI for joint filers (IRS, IRC section 1411, 2026).

The 30-day clock, and why it is not the ISO/AMT decision

The window is short and it is hard. Per the Form 15620 instructions, “An 83(b) election must be filed no later than 30 days after the date the property was transferred” (IRS, Instructions for Form 15620, Rev. 4-2025). The clock runs from the grant date for restricted stock, or from the exercise date if you early-exercise unvested options. There is no extension for a good reason and no do-over, and once made the election cannot be revoked except with the consent of the IRS (IRS Form 15620, Rev. 4-2025). Miss it, and you are back to being taxed at ordinary rates on each vest’s then-current value.

This is a different lever from the ISO/AMT question, and people mix them up. The alternative minimum tax issue is about exercising incentive stock options and the spread that creates. The 83(b) election is about when restricted stock or early-exercised shares get taxed. You can face both in the same career, sometimes in the same year, but they are separate decisions with separate math. We covered the exercise side in how the AMT actually gets triggered when you exercise ISOs in biotech.

One more distinction, because it trips up people leaving a public company for a startup. RSUs at a public company generally cannot take an 83(b) election at grant, because a restricted stock unit is a promise to deliver shares later, not a transfer of property now. The 83(b) election applies to actual restricted stock and to early-exercised options, not to standard public-company RSUs.

83(b) filed vs. not filed, side by side

The table below uses a hypothetical to keep the mechanic clear. Say a pre-clinical San Diego startup grants a founder 200,000 shares of restricted stock at a $0.001 grant-date value (a $200 total value), vesting over four years, and the shares are worth $2 each by the time the final slice vests. This is illustrative only, not a projection.

	83(b) election filed (within 30 days)	No 83(b) election
When you are taxed	Once, at grant	At each vesting date, year by year
Amount taxed	Grant-date value ($200 in the example)	Value at each vest (up to $400,000 total in the example, as the price climbs to $2)
Tax rate on that amount	Ordinary rates, top 37% for 2026, on a near-zero amount	Ordinary rates, top 37% for 2026, on each vest’s full value
Long-term capital gains clock	Starts at grant; one-year mark reached sooner	Starts at each vest; each slice waits its own year
Later sale of appreciated shares	Gain over grant-date value taxed at long-term rates, top 20% (plus 3.8% NIIT if applicable)	Gain over each vest-date value, long-term only after holding each slice a year
If the shares fail or you leave early	Tax already paid is not recovered	No tax was prepaid, so nothing to lose on unvested shares

Restricted stock: 83(b) filed vs. not filed. Rates from IRS, Rev. Proc. 2025-32 (tax year 2026); 30-day rule from IRS Form 15620 (Rev. 4-2025); holding period from IRS Topic no. 409.

Read across the “amount taxed” row and the appeal is obvious for early-stage equity. You pay ordinary tax on $200 today rather than on as much as $400,000 spread across four vesting years. Read down the last row and the risk is just as real.

The part that makes this a genuine two-sided decision

Here is where the honest version departs from the pitch. Prepaying the tax only pays off if two things happen: the shares appreciate, and you stay long enough to vest. If the company folds, or the science does not clear a trial, or you leave before your shares vest, the tax you paid at grant does not come back. You do not get to unwind the election because the outcome disappointed.

So the election is strongest when the grant-date value is genuinely small, when you believe in the company enough to plan on vesting, and when the prepaid tax is an amount you can lose without it mattering. It is weakest when the grant-date value is already high (a later-stage company), because then you are writing a real check now for a bet that has not paid off. That is the condition under which filing would be the wrong move, and it is worth naming out loud before the 30 days run.

The dollars here rarely sit in isolation. Equity timing tangles with your cash needs, your other income, and the rest of your tax plan for the year, including moves like a mega backdoor Roth if your plan allows it. If you want a second read on an equity grant before the clock runs, you can book a time to talk it through.

What to confirm before the 30 days run

A few things to evaluate with your CPA or attorney, not to treat as settled:

Confirm the grant or early-exercise date, because that is when the 30-day clock starts.
Confirm the grant-date fair market value with the company, since that is the amount you would be taxed on.
Confirm whether you actually hold restricted stock or early-exercised options (eligible) versus standard RSUs (generally not eligible at grant).
Evaluate whether you can afford to lose the prepaid tax if the shares never vest or never appreciate.
Keep proof of timely filing; the election is filed with the IRS and a copy goes to the company.

Frequently asked questions

What happens if I miss the 30-day 83(b) deadline?

You lose the election for that grant. The IRS rule is that the election must be filed no later than 30 days after the property was transferred, and it is not extended for a good reason or missed by mistake. You are then taxed at ordinary rates on each vesting slice at its then-current value, which is the outcome the election was meant to avoid.

Can I file an 83(b) election on RSUs at a public company?

Generally no. A restricted stock unit is a promise to deliver shares later, not a transfer of property now, and the 83(b) election applies to an actual transfer of restricted stock or to early-exercised options. This is a common point of confusion for people leaving a public employer for a startup, so confirm which type of equity you hold before assuming an election is available.

Is the 83(b) election the same as the ISO/AMT decision?

No. The alternative minimum tax question is about exercising incentive stock options and the spread that creates. The 83(b) election is about when restricted stock or early-exercised shares are taxed. They are separate decisions with separate math, even though a biotech employee can face both. Coordinate them rather than treating either in isolation.

Do I get my prepaid tax back if the company fails or I leave before vesting?

No. If the shares later become worthless or you leave before they vest, the tax you paid at grant is not recovered, and the election cannot be revoked except with the consent of the IRS. That is why the election is a genuine two-sided decision and works best when the grant-date value is small and you plan on vesting.

Before your window closes

The 30 days start the day the equity is transferred, and once they pass the choice is made for you. If you have a restricted stock grant or are weighing an early exercise at a San Diego startup, our biotech and life-science financial planning page is the place to start, and a complimentary review can put the numbers next to the rest of your tax picture before the clock runs out.