Founder Vesting and the 83(b) Election Explained (2026)

Founder vesting means the company can buy back a founder's unvested shares at the price paid if the founder leaves early, usually over four years with a one-year cliff. Because vesting shares are restricted property for tax purposes, founders file an 83(b) election within 30 days of buying them, so they are taxed on the shares' tiny value today instead of on their growing value each time a batch vests.

Definition: An 83(b) election is a filing under Section 83(b) of the Internal Revenue Code in which a person who receives stock subject to vesting chooses to include its value in income at the time of transfer, rather than as the shares vest. The statute requires filing no later than 30 days after the transfer, and the election generally cannot be revoked.

We'd treat both as close to essential. Vesting is cheap to put in place at formation and expensive to add later. A missed 83(b) is usually worse. Almost everything else in a company's formation paperwork can be repaired with money and a lawyer. The 30-day window can't be reopened.

Why we favor founder vesting, the CEO included

Every founder benefits from vesting, in our view, including the one who runs the company. Three reasons carry the argument for us.

It protects the founders who stay. Picture three founders where one walks away after six months and the other two build the company for years. Without vesting, the departed founder shares equally in any sale. With vesting, most of those shares return to the company, where they can be used to hire the replacement.
It's what most investors expect. Early investors are mostly backing the people. They don't want to fund a team whose members could leave with their full stake a month after the wire lands.
It sets the standard for everyone you hire. Employees will vest their options. That's a hard ask if the founders hold fully vested stock.

Four years with a one-year cliff, and an 83(b) filed on time, is also the pattern we've laid out in our guide to splitting startup equity. For how to decide the percentages before any of this happens, see our companion guide on how to split equity between co-founders.

"But we've worked together for years, and I'm a solo founder anyway"

These are two of the most common objections, and both have a fair point. A team with a long history has already shown it can hold together. A solo founder has no co-founder to protect against. Vesting can feel like a contract written for strangers.

But the painful case isn't a stranger walking off. It's a burned-out founder leaving with a large stake while the others carry the load, and that happens to long-time teams too. Fixing it later is costly once the stock price has risen. Solo founders may want to vest as well: many investors find founder stock without vesting unattractive for the same reasons, and it helps to lead by example when you start granting options.

How founder vesting works: cliff, monthly vesting and repurchase

Founders buy their stock outright at formation through a restricted stock purchase agreement, typically paying a fraction of a penny per share and sometimes contributing their existing IP as part of the price. You own the shares from day one and can vote all of them. What vests is the company's right to take them back.

Schedule. The common market pattern is four years with a one-year cliff. Nothing vests for the first 365 days, 25 percent vests at the one-year mark, and 1/48 of the total vests each month after that until everything has vested at four years.
Repurchase. If a founder leaves, the company can buy back the unvested shares, usually at the price originally paid, so there is no gain built in.
Documentation. The schedule, the repurchase right and any acceleration belong in the stock purchase agreement and in a written founder agreement that all founders sign. Read every provision before you sign. This is the document that decides what you keep.
New co-founders. Adding a co-founder a year in doesn't reset anyone else's schedule. The newcomer starts their own four years on their own start date.
Investor re-vesting. At a priced round, an investor may ask founders with little vesting left to add time, often another year. How much you give depends on your leverage.

Restricted stock isn't the same as a stock option. Check the fine print of any equity you receive to see whether you're getting shares now or a right to buy them later. The 83(b) election applies to shares you actually receive subject to vesting, which for founders means restricted stock.

The 83(b) election explained: what the tax code actually says

Section 83(a) of the tax code says that when you receive property in connection with services, you are taxed on its fair market value minus what you paid, in the first year the property is transferable or no longer subject to a substantial risk of forfeiture. Section 83(c) defines that risk as rights conditioned on future substantial services, which is exactly what vesting is. So by default, each vesting installment is a taxable event, measured at the value on that date.

Section 83(b) lets you choose instead to include the value in income at the time of transfer. The key rules, from the statute and the Treasury regulations at 26 CFR 1.83-2:

Deadline. The regulations require the election to be filed no later than 30 days after the date the property was transferred. It may even be filed before the transfer. Count calendar days from the day you buy the stock, not business days.
What you are taxed on. The fair market value at transfer, ignoring vesting restrictions, minus the amount paid. If you pay full value, as founders buying at formation usually do, the taxable amount is zero.
Forfeiture. If you later forfeit the shares, the statute allows no deduction for that forfeiture. If you paid tax on an 83(b) and then leave before vesting, that tax is gone.
Revocation. The election cannot be revoked without IRS consent, and the regulations limit consent to a mistake of fact about the transaction, requested within 60 days of discovering it. A mistake about value, or a later decline in value, does not qualify.
Paperwork. You file with the IRS and give a copy to the company. Since January 1, 2016, the regulations no longer require attaching a copy to your tax return.
Holding period. Under 26 CFR 1.83-4(a), when you make the election your holding period begins just after the transfer, which is what lets a later sale qualify for long-term capital gains treatment sooner.

Worked example: taxes with and without an 83(b) election

This is an illustrative calculation, recomputed in Python. It is not tax advice, and it ignores state tax, the net investment income tax, AMT and any QSBS exclusion.

Assumptions. A founder buys 4,000,000 shares at $0.0001 each, paying $400, which equals fair market value on the purchase date. Shares vest over four years with a one-year cliff. To keep the arithmetic readable, each year's 1,000,000 vested shares are valued at a single fair market value for that year: $0.10 in year one, $0.40 in year two, $1.00 in year three and $2.00 in year four. The founder sells all shares at $5.00 each more than a year after the final installment vests. We assume a 35 percent ordinary income rate and a 20 percent long-term capital gains rate.

Without an 83(b) election, each vesting year creates ordinary income equal to the vested shares times the value minus the price paid:

Vesting year	Value per share	Ordinary income	Tax at 35%
Year 1 (cliff)	$0.10	$99,900	$34,965
Year 2	$0.40	$399,900	$139,965
Year 3	$1.00	$999,900	$349,965
Year 4	$2.00	$1,999,900	$699,965
Total		$3,499,600	$1,224,860

That $1,224,860 is owed as the shares vest, years before any sale, on stock you can't easily sell. At the sale, your basis is the $400 paid plus the $3,499,600 already taxed, so the capital gain is $16,500,000 and the capital gains tax is $3,300,000. Total federal tax: $4,524,860.

With an 83(b) election filed within 30 days of purchase, the taxable amount at purchase is $0.0001 minus $0.0001 times 4,000,000 shares, which is zero, and nothing is taxed at vesting. At the sale, the gain is $20,000,000 minus $400, or $19,999,600, taxed at 20 percent: $3,999,920.

The difference. The election saves $524,940 in this example. More important, it removes $1.22M of tax bills that would arrive with no cash to pay them. Those vesting-date liabilities can also create tax obligations for the company, which is why acquirers and investors check for 83(b) proof in diligence.

When the election costs something. If a co-founder joins a year later and buys 1,000,000 restricted shares at $0.0001 when the fair market value is $0.10, the 83(b) creates $99,900 of ordinary income up front, about $34,965 of tax at our assumed rate, which is lost if they leave before vesting. That's a real trade-off to discuss with a tax advisor, and one more reason to issue founder stock as early as possible, when the value is lowest.

How to file an 83(b) election in 2026, step by step

The mechanics changed in 2025. The IRS lists Form 15620, Section 83(b) Election (revision April 2025), among its mobile-friendly forms, posted June 29, 2025. As of September 2026, the IRS listing shows that the form requires an IRS Online Account, which is how you sign it electronically, and that after completing it you can submit it online or download a copy for mailing. Paper filing on Form 15620 or a written statement remains valid.

Buy the stock and date it correctly. Date the restricted stock purchase agreement the same day as your payment, so there is no doubt about when the 30 days started.
Count 30 calendar days and aim to file in the first week. Planning to use the last day leaves little room for problems.
Gather the details. The form asks for a description and number of shares, the transfer date, the vesting restrictions, the fair market value at transfer and the amount paid.
Choose one filing method. Online through your IRS Online Account, or by mail to the IRS office where you file your return. Goodwin notes the online form asks you to confirm you have not already mailed an election for the same shares, and that the IRS warns against using both methods.
Check the online form's limits. Sidley Austin reported in August 2025 that the online tool first accepted at most 999,999 shares per submission and only two decimal places for prices, a problem for $0.0001 founder stock; its October 2025 update says the IRS expanded this to four decimal places and up to 99,999,999.99 securities. Check that your numbers fit before you rely on online filing.
Keep proof. Save the IRS confirmation page or PDF. For paper filings, use a trackable delivery method and keep the receipt, because investors and acquirers often ask for it.
Give the company a copy. The regulations and Form 15620 both require a copy to the company. We suggest the company store a signed, dated copy permanently in its shared records, not in one founder's inbox.

If you incorporated through a formation platform, it will usually walk you through this. See our guide on how to incorporate your startup for where the election fits in the formation sequence.

Founder vesting and 83(b) checklist

[ ] Restricted stock purchase agreement signed, dated the same day as payment
[ ] Vesting: 4 years, 1-year cliff, monthly after, with the start date stated
[ ] Repurchase price for unvested shares written into the agreement
[ ] Acceleration terms (if any) agreed and written down
[ ] IP assignment (CIIA) signed by every founder
[ ] 83(b) filed within 30 calendar days, online or on paper, not both
[ ] IRS confirmation or proof of mailing saved
[ ] Signed copy delivered to the company and stored in shared company records
[ ] Election noted in the cap table and due diligence folder

Our take on acceleration, re-vesting and when you don't need an 83(b)

Double-trigger acceleration is usually the more realistic ask. Single-trigger acceleration (vesting speeds up on one event, such as a sale) is not the norm, even for founders and key executives, while double-trigger acceleration (a sale plus a termination, usually within 9 to 18 months after closing) has become very popular with early-stage companies, as Cooley GO's guide by Craig Jacoby (last reviewed April 20, 2022) documents.

Investors resist single-trigger terms because an acquirer that needs the team to stay would then have to fund bigger retention packages, which can reduce the price paid to all stockholders. One detail founders often miss: double-trigger only helps if the acquirer assumes or continues the award, so check that your documents address that case.

Expect a re-vesting request if you're far along. If most of your stock has vested by the first priced round, the lead investor may well ask you to add time. We'd treat the amount as a negotiation driven by leverage, and have counsel check the tax effects before you agree.

Know when no 83(b) is needed. If your shares are fully vested when you receive them, there is no substantial risk of forfeiture and no election to make. The election matters when shares are subject to vesting, including options exercised early before they vest, which our equity incentive plan guide covers for employees. Once the company grants options, a 409A valuation sets the fair market value that would feed any later 83(b) calculation.

Founder vesting and 83(b) mistakes to avoid

No vesting because the team has worked together for years. A common excuse, and it hurts most when a founder burns out.
Missing the 30 days. There's usually little you can do afterward; the mitigation options tax lawyers have tend to be painful and expensive.
Signing without reading. Understand every provision of your founder stock purchase agreement.
Filing twice or not at all. Pick online or paper, then confirm it went through.
The company has no copy. Y Combinator's own legal and finance team has seen financings and acquisitions fall apart over missing 83(b) proof.
Agreeing to single-trigger acceleration without thinking about a sale. It can cost you at exit, though views differ on how much.

These documents are part of the diligence a lead investor runs before a check. 1752vc's Accelerate program invests $100K at a valuation cap of up to $3.5M in early-stage startups ready to grow, and its founder-led sales training and 850+ investor network are most useful to a company whose ownership records already hold up. It is remote with rolling admissions: Accelerate.

The bottom line

Put founder shares on a four-year schedule with a one-year cliff, file the 83(b) in the first week rather than the last, and keep the proof where the company can find it. None of it is hard. It's just unforgiving if you skip it.

Vesting is a promise to stay. The 83(b) is a letter you can't send late.

Key takeaways

Founder shares commonly vest over four years with a one-year cliff, with the company able to repurchase unvested shares.
Without an 83(b) election, every vesting installment is taxed as ordinary income at its value on that date.
The IRS requires the election within 30 days of the transfer, it generally cannot be revoked, and a copy goes to the company.
Since mid-2025 you can sign and submit Form 15620 online through an IRS Online Account, or still file on paper.
Double-trigger acceleration is common for founders; single-trigger acceleration is rarer and can hurt a sale.

Frequently asked questions

What is an 83(b) election in simple terms?

It is a one-page filing that tells the IRS to tax your restricted shares now, based on today's value, instead of taxing each batch as it vests. Founders who buy stock at a fraction of a cent usually owe nothing when they file, and any later growth is taxed only when they sell, generally as capital gains.

Can I file an 83(b) election online?

Yes. The IRS lists Form 15620 as a mobile-friendly form that you complete and sign through an IRS Online Account, then submit online or download for mailing. The IRS warns against using both methods, so pick one, save the confirmation, and give the company a copy. The 30-day deadline is the same whichever way you file.

Do I need an 83(b) election if my founder shares are fully vested?

No. The election applies to property subject to a substantial risk of forfeiture, such as shares that vest over time. Fully vested shares are taxed when you receive them on any value above what you paid. Most investors expect founder shares to vest, though, so a fully vested founder is unusual in a venture-backed startup.

Can investors make founders re-vest their shares?

They can ask, usually at the first priced round. Investors sometimes want founders with little vesting left to add time, often a year, and how much you accept depends on your leverage. A new schedule on already-vested shares is a negotiation, and any re-vesting should be discussed with counsel for tax effects before you sign.

What is double-trigger acceleration for founders?

It speeds up vesting only if two things happen: the company is sold and the founder is terminated, usually within 9 to 18 months after closing, per Cooley GO. It protects a founder pushed out after an acquisition without scaring buyers, which is why it is far more common than single-trigger acceleration.

Sources

Disclaimer: This guide is for general education only and is not legal, tax or investment advice. Laws, market data and program terms change, so it may not reflect the latest developments or fit your situation. Treat it as a starting point, not a source of truth, and talk to a qualified lawyer, accountant or financial adviser before you make decisions.