The two paperwork mistakes that cost founders millions

Last month a founder called us six months after incorporation. He'd just gotten a term sheet at a $12M valuation. His lawyer told him he owed the IRS $340,000 in taxes on shares he couldn't sell yet. He'd missed the 83(b) election deadline by four months.

The math on missing 83(b) or getting 409A wrong is brutal. We're walking through both, with the actual numbers that show what they cost.

The 83(b) election and why it exists

When you receive restricted stock that vests over time, the IRS normally taxes you as each chunk vests. If your company grows, that means you're paying ordinary income tax (up to 37% federal plus state) on increasingly valuable shares you can't sell yet.

An 83(b) election flips this. You elect to pay tax on the full grant value at the time you receive it, when the fair market value is usually a fraction of a cent per share. Everything after that is capital gains when you eventually sell.

The provision exists because the IRS doesn't want people gaming the system by backdating when they "received" stock. So they give you 30 days to make the election, and if you miss it, you're stuck with the default treatment.

Section 83(b) of the Internal Revenue Code is the actual text. It's three paragraphs. The 30-day deadline is in subsection (b)(2).

You have 30 days from grant date. Not 31.

The election must be filed with the IRS within 30 days of the date you received the stock. Miss it by a day and the IRS will not accept it. There's no extension, no appeal, no "we didn't know" exception.

We see founders miss this three ways:

Scenario one: Founder incorporates on day zero, issues themselves 5 million shares with four-year vesting, then reads about 83(b) six months later when they're talking to investors. Too late. They're now on the hook for ordinary income tax on every share that vests, at whatever the 409A valuation says those shares are worth.

Scenario two: Founder hires a critical early engineer, grants them 200,000 shares with vesting, doesn't mention 83(b) because they assume the lawyer or Carta will handle it. The engineer doesn't file. Two years later the company raises a Series A and the engineer's shares are suddenly worth $1.50 each on paper. They owe taxes on $300,000 of income they never received in cash.

Scenario three: Founder raises a seed round and takes new restricted stock as part of the recap. They filed 83(b) at formation but don't realize they need to file again for the new grant. Same disaster.

The IRS doesn't care that you didn't know. The deadline is statutory.

What missing it actually costs

Real example from our portfolio, numbers adjusted slightly but math is exact:

Founder grants herself 4.8 million shares at $0.00012 per share at company formation. Standard four-year vest with one-year cliff.

Two years later the company has grown. They've shipped product, signed their first enterprise customers, and are raising a Series A. The 409A valuation now says common stock is worth $0.94 per share.

In year two, she vests 1.2 million shares (the cliff year plus six months of monthly vesting).

If she filed 83(b) on day zero

Tax due at grant: 4.8M × $0.00012 = $576 of ordinary income. She pays roughly $215 in federal and state tax.

Tax due as shares vest over four years: $0.

Tax due when she eventually sells: Long-term capital gains on the spread between sale price and $0.00012 basis. Federal rate is 20% plus 3.8% net investment income tax, so 23.8% total.

If she didn't file 83(b)

Tax due at grant: $0.

Tax due in year two as 1.2M shares vest at $0.94 FMV: $1,128,000 of ordinary income. At 37% federal plus 13.3% California state, she owes $568,000 in taxes. She doesn't have $568,000. She has illiquid shares in a private company.

This continues every year as more shares vest. By year four, assuming the valuation holds or grows, she's paid over $2 million in ordinary income tax on shares she can't sell.

The cost of missing the 83(b) election on a successful startup is typically $1.5M to $3M in avoidable taxes for a founding team. We've seen it go higher.

How to file it correctly

You need to do five things, in order:

Receive the stock grant. The 30-day clock starts the day the board approves the grant and you sign the stock purchase agreement, not the day you hear about it.

Fill out the 83(b) election form. It's a one-page document. The IRS doesn't provide an official form; you use the format from Notice 2005-1. Stripe Atlas, Carta, and every startup law firm have templates.

Mail it to the IRS within 30 days. Certified mail, return receipt requested. The postmark date is what counts, not when the IRS receives it. Keep the certified mail receipt and the return receipt forever.

Give a copy to the company. They need it for their records and for your W-2 reporting.

Attach a copy to your federal tax return for the year of the grant.

If you formed through Stripe Atlas, this is automatic. If you used Gunderson or Cooley, they'll walk you through it. If you incorporated yourself, set a calendar reminder for day 15 and day 25 after any stock grant.

The 409A valuation and what it's for

A 409A valuation is an independent appraisal of your common stock's fair market value. You need it to set the strike price for employee stock options.

If you grant options with a strike price below fair market value, those options are treated as deferred compensation under Section 409A of the tax code. The employee pays ordinary income tax plus a 20% penalty plus interest at vesting, even if they haven't exercised yet. This destroys the entire point of options.

The safe harbor rule says that if you have an independent 409A valuation done within the past 12 months, the IRS will presume you used the correct FMV unless they can prove otherwise. Without a 409A, the burden of proof is on you.

When you need one

Before your first option grant. Even if it's to your co-founder or your first engineer. The IRS doesn't care that you're three people in a garage.

After any material event: a priced equity round, a secondary sale, a major customer contract that changes your revenue trajectory, an acquisition offer even if you don't take it. "Material event" is vague on purpose. If something happened that would make an investor pay more per share than they would have last month, you need a new 409A.

Annually, even if nothing material happened. The safe harbor expires after 12 months. Letting your 409A lapse and then granting options is the same as not having one at all.

What it costs and who does them

Carta bundles 409A valuations into their cap table service. If you're already a Carta customer, it's included. If you're not, you're paying $2,000-$3,000 per year for cap table management and the 409A comes with it.

Sharp 409A charges $1,200-$1,800 per valuation depending on complexity. Aranca and Solium are in the same range.

Big Four accounting firms (Deloitte, PwC, EY, KPMG) charge $5,000-$15,000. You don't need this until you're post-Series B or in a regulated industry where the extra credibility matters.

Use Carta or Sharp 409A for seed and Series A. The Big Four are expensive overkill at this stage.

How 83(b) and 409A fit together

They're solving different problems:

83(b) is for restricted stock. Founders and early employees who receive actual shares that vest over time. You file 83(b) to lock in the tax basis at grant.

409A is for stock options. Employees who receive the right to buy shares at a future date. You need a 409A to set the strike price at or above fair market value.

Restricted stock grants to employees also need 83(b). If you give an early hire 50,000 shares of restricted stock instead of options, they need to file 83(b) within 30 days just like a founder would.

The mistake we see: founder files 83(b) for themselves at incorporation, then assumes they're "done" with 83(b). They grant restricted stock to their first engineer and don't tell them to file. Two years later the engineer has a five-figure tax bill.

The mistakes that actually happen

Missing the 83(b) deadline is the single most expensive paperwork error in startup formation. We've seen it cost individual founders over $2 million.

Granting options without a current 409A. If your 409A expired 13 months ago and you granted options last week, those options are potentially subject to Section 409A penalties. The employee is the one who pays, not the company, which makes this worse.

Filing 83(b) but not keeping proof. If the IRS loses your form (this happens), you need the certified mail receipt to prove you filed on time. We've seen founders have to hire tax attorneys to fight this because they didn't keep the receipt.

Not filing 83(b) for new restricted stock at later rounds. If you take new founder shares as part of a Series A recap, those are a new grant. You need to file 83(b) again.

Setting option strike prices below the 409A FMV because "it's better for the employee." It's not. It triggers the 409A penalty tax, which is worse than just paying ordinary income tax would have been.

The full formation checklist

Delaware C-Corp formation. We covered why Delaware here.

Founder stock issued with vesting, typically four years with a one-year cliff.

83(b) election filed within 30 days, sent certified mail, receipt kept forever.

EIN from the IRS for tax purposes.

US bank account. Mercury, Brex, or SVB for startups.

409A valuation before any option grants. Carta or Sharp 409A.

Cap table on Carta, Pulley, or AngelList.

Annual 409A refresh calendared for 11 months out.

Annual Delaware franchise tax filing calendared for March 1.

If you formed less than 30 days ago and haven't filed 83(b) yet, do it today. If you formed more than 30 days ago and didn't file, talk to a tax attorney about damage control. If you have options outstanding without a current 409A, get one this week.

The paperwork sounds boring until it costs you $2 million. We help founders get this right before they raise. Book a call if you want to make sure you're not the next person who has to write that check.