Imagine waking up one Tuesday to a tax bill of $400,000 — not because you sold anything, not because you took home a dollar of cash, but because a piece of paper in your company's cap table got more valuable while you slept. That is the phantom tax problem that the Internal Revenue Code's Section 83(b) election was designed to solve. For founders, very early employees, and anyone exercising stock options early, it is arguably the single most consequential tax form you will ever sign — and you have just 30 days to file it.
Miss the deadline and there is no apology letter, no reasonable-cause exception, no quiet workaround. The election simply ceases to exist for that grant of stock. Yet every year, otherwise sophisticated startup people miss this window, sometimes because they did not know it existed, sometimes because they assumed their lawyer or HR team handled it, sometimes because they conflated the start date with the date the board actually approved their grant. This guide walks through the mechanics, the math, the new IRS Form 15620 online filing portal that went live in 2025, and the cases where filing is actually the wrong move.
What Section 83(b) Actually Does
Section 83 of the Internal Revenue Code governs how property transferred in connection with the performance of services is taxed. The default rule under Section 83(a) is straightforward and brutal: if your stock is "substantially nonvested" (meaning subject to forfeiture if you leave), you pay ordinary income tax on the spread between fair market value and what you paid every time a portion of it vests. That sounds harmless when shares are worth pennies. It becomes a nightmare when a hot startup raises a Series B at a $1 billion valuation and your unvested chunk silently appreciates by orders of magnitude before it vests.
Section 83(b) lets you flip that switch. By filing the election within 30 days of receiving the property, you tell the IRS: tax me now, at today's fair market value, on the entire grant — even the unvested portion. You voluntarily accept ordinary income tax (often zero or near-zero) on the front-end spread, in exchange for starting the capital-gains clock immediately and freezing your ordinary-income exposure at today's number. Everything that happens after that, every dollar of appreciation, is taxed as long-term capital gain when you eventually sell, assuming you hold for more than a year.
That single decision can mean the difference between paying 37% federal ordinary rates on millions of dollars of phantom income across multiple years and paying 20% long-term capital gains on a single liquidity event.
Who Should Care About 83(b)
The election is relevant any time three conditions line up: you receive property (almost always stock) in connection with services, the property is subject to a "substantial risk of forfeiture" (typically a vesting schedule), and you have the chance to pay tax now on the unvested portion. In practice that means:
- Founders receiving restricted stock at incorporation that vests over four years with a one-year cliff. This is the textbook case. Stock at incorporation is typically worth a fraction of a cent; the 83(b) makes the recognized income negligible.
- Very early employees receiving restricted stock awards (RSAs) rather than options, where the share price is still close to par value.
- Option holders exercising early. If your plan allows early exercise of unvested options (common at seed-stage companies), you must file 83(b) within 30 days of the exercise date to start the capital gains clock on the unvested shares you just acquired.
- Recipients of profits interests in LLCs — under Rev. Proc. 93-27 and 2001-43, an 83(b) is often filed defensively to confirm zero value at grant.
You should not file an 83(b) for restricted stock units (RSUs). Despite the similar name, an RSU is a contractual promise to deliver shares later, not a transfer of property today, so there is no property to elect on. Filing one for RSUs has no legal effect but causes administrative confusion for years.
The Phantom Tax Problem, in Numbers
Picture a founder, Maya, who is granted 8,000,000 shares of restricted common stock at incorporation. The board sets the par value at $0.0001 per share. Maya pays $800 to buy the shares outright, subject to a standard four-year vest with a one-year cliff. At grant date, fair market value equals what she paid: $800. No tax due either way.
Scenario A — Maya files Section 83(b) within 30 days. She reports $0 of ordinary income (FMV minus amount paid). Her holding period for capital gains begins immediately on all 8 million shares. Three years later, the company is acquired and her shares are worth $5 per share, or $40 million total. She sells at acquisition. Her gain: $40,000,000 minus her $800 basis, taxed at long-term capital gains rates. Federal tax at 20%, plus 3.8% net investment income tax, roughly $9.5 million.
Scenario B — Maya forgets to file the 83(b). Each vesting tranche triggers ordinary income tax on the spread between FMV at vest and the $0.0001 she paid. Year 1 cliff vests 2,000,000 shares when the company has just raised a Series A and the 409A valuation has shares at $0.50. Ordinary income that year: roughly $1 million. Year 2 vests another 2 million shares at $1.50 FMV — $3 million ordinary income. Year 3 vests 2 million at $3.00 FMV — $6 million. Year 4 the company is acquired and the last 2 million vest at $5.00 — another $10 million ordinary income. Total ordinary income recognized: $20 million, taxed at federal rates that top out at 37%, plus state, plus Medicare. Then when she sells at acquisition, only post-vest appreciation gets the capital gains rate. Her total federal tax burden could easily exceed $8 million in ordinary income tax alone — and she had to pay much of it years before she ever saw a dollar of cash from the company.
That second scenario is the phantom tax bill. Maya owes tax on paper gains long before she can sell anything, often with no liquidity to pay the bill except by selling shares — which she may not be able to do because the company is still private. The 83(b) election is the cleanest way to eliminate that nightmare for stock that has appreciation potential and a low starting value.
The 30-Day Filing Deadline Is Absolute
The 30-day window runs from the date the property was transferred, not the date you signed paperwork, not your start date, not when you finally got around to opening the email from your lawyer. For founders, the transfer date is typically the date the board approves the issuance and you pay for the shares. For early-exercising option holders, it is the date you exercise.
The deadline is counted in calendar days, including weekends and holidays. The only adjustment: if day 30 lands on a Saturday, Sunday, or federal holiday, the deadline moves to the next business day. Otherwise the window is unforgiving. There is no reasonable-cause exception, no first-time-abate program, no waiver for good intentions. Tax courts have repeatedly upheld late-filed elections as invalid even when the failure resulted from professional malpractice.
Treat day 30 as a hard wall. A reasonable rule of thumb at well-run companies: if you receive any restricted stock or exercise an early-exercise option on a Monday, file the election by Friday of the same week. Build the buffer. There is no upside to procrastination and the downside is potentially seven figures of unnecessary tax.
Filing in 2026: Form 15620 and the New Online Portal
For decades, the 83(b) election was a self-drafted letter — you wrote a one-page statement on plain paper, mailed it certified to the IRS service center where you file your taxes, and prayed the return-receipt card actually came back. The 2024–2025 modernization changed this. The IRS released Form 15620 in late 2024 as a standardized election form, and in July 2025 it opened an online filing portal that lets taxpayers submit electronically through the IRS website.
Here is what the modern filing flow looks like in 2026:
- Create or sign in to your IRS online account using ID.me identity verification. If you do not already have an ID.me account, allow a day or two — verification can require a video call or document upload.
- Complete Form 15620 in the IRS portal. You will enter your legal name, Social Security number, the transfer date, a description of the property (e.g., "8,000,000 shares of common stock of Acme Inc."), the fair market value at transfer, the amount you paid, and the name and address of the transferor (your company). The portal now supports prices up to four decimal places (essential for par-value common at $0.0001) and quantities up to 99,999,999.99 shares.
- Submit electronically or download and mail. Online submission is the IRS's preferred method, but a paper Form 15620 mailed via USPS certified mail with return receipt remains valid. Do not do both — duplicate filings create processing delays.
- Give a copy to your company. Treasury regulations still require you to furnish a copy of the filed election to the entity that transferred the stock. Email the PDF to your finance or general counsel contact and ask for written confirmation of receipt.
- Keep the proof of filing forever. Save the IRS acknowledgement (online) or the certified-mail return-receipt card and a copy of the form. If the IRS ever questions whether the election was timely, this is your only evidence. Founders have lost tax fights they should have won because a lawyer's file got lost in a server migration five years later.
You no longer have to attach the election to your tax return, but you should still mention it in any conversations with your CPA before the April filing deadline, because the election affects how your W-2 reports compensation income that year.
When Filing 83(b) Is the Wrong Move
The election is not a free option — it requires you to pay tax today on the spread between FMV and your purchase price. When that spread is meaningful, the math gets ugly fast.
Consider an employee who joins a Series C company that has been around for years and gets a restricted stock award with an FMV of $50 per share on 100,000 shares — a $5 million spread. Filing 83(b) immediately generates $5 million of ordinary income, which at top federal and state rates is roughly $2 million of cash tax due in the next April. If the company fails before the shares vest — or the employee leaves and forfeits unvested shares — the IRS provides no refund for the tax already paid on forfeited shares. That is the most important asymmetry in the entire decision: you cannot recover taxes paid on stock you later lose.
So skip the election when:
- The spread is large. If FMV materially exceeds your purchase price at grant, the up-front tax cost may swamp the future benefit.
- The risk of forfeiture is real. If you might leave the company before vesting, or the company might fold, you are paying tax on shares you may never own.
- The grant is RSUs. No transfer of property, no election available.
- You cannot afford the tax. Founders sometimes file 83(b) and then discover they owe more cash than they have. Plan the funding before you file.
The decision generally tilts toward filing when the spread is near zero (founders at incorporation, very early employees on low-priced RSAs, early-exercising options at the strike price). It tilts away when the spread is large or the forfeiture risk is high.
Interaction With ISOs, NSOs, and QSBS
For non-qualified stock options (NSOs), exercising an unvested option creates a transfer of restricted stock; an 83(b) filed within 30 days fixes ordinary income at the spread on the exercise date and converts future appreciation to capital gains. Without the election, each vesting tranche triggers ordinary income on the then-current spread.
For incentive stock options (ISOs), the 83(b) election interacts with the alternative minimum tax (AMT) rather than regular income tax. Filing an 83(b) on early-exercised ISOs sets the AMT preference item at the spread on the exercise date for the entire grant, rather than spreading it across vesting events. This can be advantageous when the spread is small, but the AMT analysis is genuinely complex and warrants a CPA review.
The election also matters for Qualified Small Business Stock (QSBS) under Section 1202. To qualify for the up-to-100% gain exclusion (up to $10 million or 10x basis), the stock must be held for five years from the date of acquisition. Filing 83(b) on early-exercised options is sometimes the only way to start the five-year clock on the full grant immediately, rather than waiting for each vesting tranche to start its own clock. For founders aiming at a long-hold QSBS strategy, the election is often a no-brainer regardless of the spread math.
Common Mistakes That Cost Founders Real Money
Even people who know the election exists trip on the details. The recurring patterns:
- Counting from the wrong date. The 30 days run from the legal transfer of property, typically the board-approval and purchase date — not the employee's start date, not the offer-letter date, not the signature date on the stock purchase agreement if it differs from the actual board approval. Read the resolutions; do not guess.
- Not filing because "the lawyer handles it." Many startup lawyers explicitly say they do not file 83(b) elections for clients because the consequence of a missed filing is catastrophic. Confirm in writing who is responsible. Default assumption: you.
- Filing for RSUs. RSUs are unfunded promises, not property. The IRS will simply ignore the election; the harm is mostly wasted time, but it can create confusion in audits years later.
- Forgetting to give a copy to the company. Required by regulation and frequently overlooked. Send the PDF and get a confirmation reply.
- Losing proof of filing. Audits can happen years later. Save the IRS acknowledgement, the form, and (if mailed) the return-receipt card in a place you control, not a corporate email account you might lose access to.
- Filing 83(b) on a co-founder's grant without coordinating. Co-founders sometimes treat 83(b) as one person's chore. Each founder must file individually within 30 days of their own grant.
- Not modeling the tax liability. A founder with a high-FMV grant who files 83(b) on auto-pilot can owe hundreds of thousands of dollars in April. Run the numbers before you mail.
A Practical Founder Checklist
When you receive restricted stock or exercise an early-exercise option, work this sequence within the first week:
- Confirm the transfer date. Get the board resolution or option-exercise notice with the precise date.
- Compute the spread. FMV at transfer minus what you paid. If the spread is zero or nominal, the case for 83(b) is overwhelming.
- Decide. Model the alternative — what the tax bill looks like if you do nothing — versus the up-front tax if you file. For most early-stage founder grants, filing is correct.
- Open or refresh your ID.me account. Verify well before day 25.
- Complete Form 15620 in the IRS portal. Double-check Social Security number, FMV, share count, and transfer date. Single digit typos have caused successful audits.
- Submit electronically. If you mail instead, use USPS Certified Mail with return receipt — no exceptions.
- Email a copy of the filed form to your company. Get a written confirmation back.
- Save everything to a folder you personally control, with a calendar reminder for the following April to flag your CPA.
Most founders can complete the entire flow in under an hour. Spending that hour can save seven-figure tax bills three years later.
Keep the Tax Story Straight From Day One
The 83(b) election is one of those decisions where the impact compounds for years before anyone notices. The same is true of the equity grants, vesting events, exercise transactions, and 409A revaluations that flow alongside it. If you only document them at tax time, you will discover gaps — a missing transfer date, a stale FMV, a forgotten promissory note — exactly when the cost of getting it wrong is highest.
The cleanest defense is a financial ledger you actually trust. Plain-text accounting captures every transaction as a line of text you can read, version-control, and search five years later — exactly the qualities you need when an IRS examiner asks for evidence of an event from 2026. Beancount.io gives you that ledger as a hosted service: every grant, exercise, vest, and sale recorded in a transparent format with full history, no vendor lock-in, and an AI assistant that understands your numbers. Get started for free and turn your equity and compensation records into something the future you (and your auditor) can rely on.
The 30-day window for an 83(b) election is short. The proof you will need to defend it is long. Build the record now.