The 30-Day Decision That Can Save Founders Millions: A Plain-English Guide to the Section 83(b) Election

Imagine paying $200 in tax today to avoid a $400,000 tax bill four years from now. That is not hyperbole. It is roughly what a Section 83(b) election can do for the founder of a fast-growing startup who receives restricted stock at incorporation, when the company is worth almost nothing, and rides that stock through a Series C valuation increase.

Now imagine missing a single 30-day filing window and watching every vesting tranche get taxed as ordinary income at the company's then-current fair market value. That, unfortunately, is also real. The IRS does not grant extensions, do-overs, or sympathy.

This guide explains what a Section 83(b) election is, who actually needs one, the mechanics of filing (including the new IRS Form 15620 online portal), and the bookkeeping habits that keep your tax position defensible years later when the term sheet finally arrives.

What Section 83 Is Really Taxing

Section 83 of the Internal Revenue Code governs property transferred to you in connection with services. If your employer hands you a stack of stock certificates because you joined the company, that grant is, by default, taxable income — measured at the property's fair market value (FMV) minus what you paid for it.

There is one nuance that creates the whole 83(b) opportunity. Section 83 does not tax property that is "subject to a substantial risk of forfeiture." In plain English, that means stock you can lose if you leave before vesting. For unvested stock, the default rule says: don't tax it yet. Wait until each tranche vests. Tax the FMV at that future moment, when restrictions lapse.

For most situations, "wait until it vests" sounds like a kindness. For founders, it is often a curse.

The default rule, illustrated

Suppose you co-found a company in January. You pay $0.0001 per share for 4 million shares of common stock, subject to a standard four-year vesting schedule with a one-year cliff. Today the FMV of each share is exactly what you paid: a tenth of a cent.

Without an election, here is what the IRS taxes you on:

• Year 1 (cliff vest, 1M shares): If the company has raised a seed round and the common is worth $0.10/share, you recognize $100,000 of ordinary income on the cliff alone.
• Years 2–4 (monthly vest): Every tranche vests at the FMV of that month. A Series A bumps common to $0.50; a Series B pushes it to $1.50. You owe ordinary income tax — at federal rates up to 37 percent, plus state — on each tiny tranche.

By the time you reach Year 4, you may have recognized millions in phantom ordinary income on stock you have not sold and may not be able to sell for years.

Enter the 83(b) Election

Section 83(b) lets you tell the IRS, in writing, "Tax me now on the full grant, at today's FMV, as if there were no vesting at all."

For our founder, the math becomes:

• Day of grant: FMV is $0.0001 × 4,000,000 = $400. Subtract what you paid ($400). Taxable spread is $0. Tax owed: $0.
• Vesting events: None taxable. The election treats the entire grant as already taxed at transfer.
• Future sale: Any appreciation above $0.0001 is a capital gain, taxed at long-term rates if you have held for more than 12 months from the grant date.

That is the magic. You pay tax now on a number close to zero, and the entire upside flips from ordinary income (up to 37 percent federal) to long-term capital gain (typically 20 percent federal, plus 3.8 percent net investment income tax in some cases).

Three benefits stacked together

1. Rate arbitrage. Long-term capital gain rates beat ordinary income rates by roughly 17 percentage points federal.
2. Timing freedom. You decide when to recognize gain — at sale, not on someone else's vesting calendar.
3. Holding-period clock starts immediately. Both the long-term capital gains clock (12 months) and, where applicable, the Qualified Small Business Stock (QSBS) clock under Section 1202 start at grant rather than at each vest.

That third point is where the math really compounds for founders.

How 83(b) Supercharges QSBS

If your company qualifies as a C corporation with under $75 million in gross assets at the time you receive your shares (a threshold expanded by the One Big Beautiful Bill Act for stock acquired after July 4, 2025), your shares may be Qualified Small Business Stock under Section 1202.

QSBS, when held long enough, can exclude up to $15 million of gain from federal tax — or 10 times your basis, whichever is greater. The OBBBA introduced a tiered holding rule for newly issued QSBS:

• 50 percent exclusion after 3 years
• 75 percent exclusion after 4 years
• 100 percent exclusion after 5 years

Without an 83(b) election, the QSBS clock arguably restarts each time a tranche vests, because each tranche is treated as a fresh acquisition. With a timely 83(b), the clock starts on the entire grant on day one. For a founder, that can be the difference between hitting QSBS treatment well before a typical exit window and missing it entirely.

For a deep dive on QSBS mechanics, see prior posts on Section 1202 and the new OBBBA thresholds. The two elections work together: 83(b) starts the clock; Section 1202 collects the exclusion.

When 83(b) Is the Right Choice

The election is most powerful when today's FMV is low and the price you paid is close to it. That describes:

• Founder common stock at incorporation
• Early employees receiving restricted stock awards (not options) before a priced round
• Restricted stock awards in a 409A valuation that is still low
• Holders of restricted stock units (RSUs) — though note that RSUs themselves are not technically Section 83 property until shares are actually issued; check with counsel before assuming an 83(b) is even an option

It is less powerful, or actively harmful, when:

• The FMV at grant is high (Series C and beyond) — you would owe real tax today on stock you cannot sell
• The company is unlikely to appreciate dramatically
• You suspect you will leave before vesting and forfeit the stock — because if you forfeit, you do not get the tax back

The 30-Day Window: Read This Twice

The election must be filed within 30 days of the transfer date. The transfer date is the date the stock is issued to you, not the date you signed the offer letter, not the date you accepted, not the date your vesting begins (those can all differ).

The 30 days are calendar days, not business days. If day 30 lands on a weekend or federal holiday, you get the next business day. Otherwise, day 30 is day 30.

Things that do not stop the clock:

• Holidays
• Travel
• A pending board approval
• Your lawyer being on vacation
• The mail being slow
• The IRS not opening your envelope yet
• Your company not countersigning the stock purchase agreement

Things that count as filing:

• Mailed with USPS Certified Mail with Return Receipt before midnight on day 30 (the postmark controls)
• Filed electronically through the new IRS Form 15620 portal before midnight on day 30

The New Form 15620: Filing Goes Online

Through November 2024, taxpayers filed 83(b) elections by mailing a homemade letter to the IRS service center where they filed their personal return. There was no official form. As of mid-2025, that changed:

• The IRS released Form 15620, Section 83(b) Election, in November 2024
• In July 2025, the IRS began allowing electronic filing of Form 15620 through IRS.gov using ID.me authentication
• Paper filing of Form 15620 is still permitted, but the IRS indicates online filing is preferred

The online form has some quirks worth knowing before you click submit. Earlier limits on price and share count have been raised: the portal now accepts a per-security price up to four decimal places ($0.0001 works) and up to 99,999,999.99 securities. Founders with tiny par-value common at large share counts can now use the online form without workarounds.

Pick one filing channel. Filing paper and filing online to be "safe" is not a defensive move — it is a way to confuse the IRS and trigger correspondence you do not want.

What the form actually asks for

Whether you file Form 15620 or write your own letter, the IRS needs:

• Your name, address, and taxpayer identification number (SSN)
• A description of the property (e.g., "1,000,000 shares of Common Stock of Acme, Inc.")
• The date of transfer (the grant date)
• The taxable year in which you are filing the election
• Any restrictions on the property (vesting schedule, repurchase rights at cost, transfer restrictions)
• The fair market value at the date of transfer
• The amount you paid for the property
• A statement that copies have been furnished to the issuer

Sign it. Date it. Send it.

The Most Common Mistakes (and How to Avoid Them)

Decades of practitioner war stories produce a consistent list of how 83(b) elections go wrong.

1. Missing the 30-day deadline

The single most common — and the most catastrophic. There are very limited paths to a fix, all of them imperfect: in extremely narrow circumstances the IRS will accept a late election under Section 9100 relief, but it is expensive, slow, and unreliable. Plan as though the deadline is absolute.

2. Filing with the IRS but forgetting the employer copy

The regulations require you to furnish a copy of the election to the entity that issued the stock. Failing to do so does not necessarily invalidate the election under current rules, but it creates payroll-reporting mismatches that resurface in audits. Hand-deliver a copy, email a signed PDF, and keep proof of delivery.

3. Filing without keeping proof

The IRS does not send you a confirmation letter when it receives your 83(b). If you mail it, use Certified Mail with Return Receipt — the green slip is your proof. If you file online, save the confirmation page and the email receipt. Without proof, an aggressive auditor years later can claim no election was made and tax every vesting tranche.

4. Filing the wrong FMV

If the FMV on the form is wrong (too low) and the IRS finds out, you will owe back tax and penalties on the difference. If it is wrong (too high), you have unnecessarily paid tax. Use the 409A valuation report — most startups have one — or the price paid by recent investors in the most recent priced round, adjusted for the discount applicable to common stock.

5. Filing when you should not

If the FMV at grant is genuinely high and the company is uncertain, the election is gambling. You are prepaying tax on stock that might never vest, that you might never be able to sell, and that you cannot get a refund on if you forfeit it. There is a reason it is irrevocable.

6. Forgetting to report the income on your 1040

The amount included by the election (FMV minus amount paid) is ordinary compensation income for the year of grant. Your employer should report it on your Form W-2; if not, you still need to include it on your individual return. For service providers who receive restricted stock without being employees, the same amount is reported on Schedule C or as other income depending on the relationship.

7. Treating an option grant as an 83(b) opportunity

A vanilla option grant is generally not Section 83 property at the time of grant — it is a right to acquire property. The 83(b) election attaches to property transfers, which means early exercise of an option followed by holding restricted stock, or a restricted stock award itself. Filing an 83(b) on a plain stock option grant accomplishes nothing.

8. Filing on the wrong service center

The election must go to the IRS service center where you file your personal return. Filing the right form at the wrong address can be treated as never filed. The Form 15620 online portal eliminates this risk; if you mail, double-check the current address for individual returns in your state.

A Worked Example: The Cost of Getting It Right Versus Wrong

Take a founder who receives 4 million shares of common at $0.0001/share, four-year vest, one-year cliff. The company appreciates roughly as follows:

Path A: No 83(b) election. Each vesting tranche generates ordinary income equal to (FMV at vest × shares vesting). Roughly $400,000 ordinary income in Year 1, then quarterly tranches at progressively higher prices through Year 4. Cumulative ordinary income at top federal rates (37 percent) plus state could easily exceed $4–5 million in tax through Year 4, payable each year out of pocket — on stock the founder cannot sell. Future sale is then taxed as capital gain only on appreciation above the price at each vest.

Path B: Timely 83(b) election. Ordinary income at grant: $0 (FMV equals amount paid). No tax at any vesting event. At sale in Year 5, the gain is $40 million minus $400, taxed at long-term capital gain rates — and if the stock qualifies for QSBS, up to $15 million of that gain may be excluded entirely.

The 83(b) election did not change the economic outcome of the business. It changed the tax bill by millions of dollars and shifted the timing from "pay every year on phantom value" to "pay once when you finally sell."

Bookkeeping and Recordkeeping: The Boring Part That Saves You

A 30-day window is short, and an exit is far. Years can pass between filing your 83(b) and proving you did so. The single best protection is disciplined record-keeping from day one.

Accurate bookkeeping for founders should treat the stock grant as a documented event with a paper trail that survives every laptop swap and every cloud-provider change. At minimum, store in one place:

• The stock purchase agreement with the grant date clearly identified
• The 409A valuation or board-approved FMV used on the form
• A copy of the signed Form 15620 (or letter)
• USPS Certified Mail receipt or the online filing confirmation
• The dated copy provided to the company
• Any W-2 or 1099 reporting the income (or notes explaining why none was issued because the spread was zero)

A plain-text accounting system that lives in version control makes this trivially auditable years later. Each event — the grant, the election filing, the proof of delivery — can be logged as a transaction with attached documentation. When an investor due-diligence questionnaire asks "did the founders file timely 83(b) elections?" in Year 6, you do not want the answer to depend on whether someone can find a five-year-old email.

Practical Decision Checklist

Before you file:

• Is the property actually Section 83 property (restricted stock or early-exercised option shares), not a plain option grant?
• Is the current FMV genuinely low, so the tax-now cost is small?
• Do you believe the company is likely to appreciate?
• Are you reasonably confident you will stay through some or all of the vesting?
• Do you have the cash (or close to it) to pay the income tax on the spread?
• Have you confirmed the exact transfer date and counted forward 30 calendar days?
• Have you chosen one filing channel — online Form 15620 or certified mail — and stuck with it?
• Have you delivered a copy to your employer with proof of delivery?
• Have you set a calendar reminder for next April to make sure the income flows correctly onto your 1040?

If you can answer yes to those, the election is almost always the right move at the founder stage and at very early employee stages.

Keep Your Equity Records Audit-Ready from Day One

The 83(b) election itself takes minutes to file, but the records around it have to survive years. As you launch a company, exercise early-stage options, or onboard your first hires with restricted stock, treat every grant, election, and FMV memo as a permanent accounting event. Beancount.io provides plain-text accounting that gives you complete transparency and version control over your financial records — no proprietary lock-in, no missing files when the diligence questionnaire arrives. Get started for free and see why founders and finance professionals are switching to plain-text accounting.