The Thirty-Day Window

There is a one-page letter you have exactly 30 days to mail to the IRS. File it, and the tax on your equity is often zero. Miss the window, and those same shares can hand you a tax bill in the millions, years before there is any cash to pay it.

It is called an 83(b) election, and it matters to anyone who buys stock before it has vested. A founder with restricted shares, an early employee, anyone who exercises their options early. Same trigger, same deadline. Yet almost nobody who needs it hears about it in time. There is no reminder, no confirmation, no second chance. The clock starts the day you buy the shares, and most people don't even know it's running.

The Setup

Surya is employee number twelve at a young startup. His offer includes a grant of 100,000 stock options at a strike price of $0.50, the price he is allowed to buy each share for.

An option is only the right to buy, not the stock itself. Normally you wait until your shares vest, earning them over four years, and exercise later. But Surya's company, like many, lets employees exercise early, buying the shares before they vest.

So Surya writes a check for $50,000 and buys all 100,000 shares up front. The shares are his, but they are restricted until they vest. The company can buy them back for what he paid if he leaves. That catch, the fact the shares can be pulled back, is the hinge the entire tax story turns on.

Because the shares can still be clawed back, the IRS doesn't consider them truly his yet. And a share the tax code doesn't consider yours yet is a share it hasn't taxed yet.

The Default

Here is what happens if Surya does nothing after exercising.

The IRS waits. It taxes each block of shares the moment it vests — not when he bought it — on the gap between his $0.50 strike and what each share is worth that day. As the startup climbs, that gap explodes.

Worse, the gap counts as ordinary income, the same category as his salary, taxed as high as 37% federal, and once state piles on, north of 50% all in. Not the gentler capital gains rate that stock is supposed to earn. Every vesting date, the run-up gets taxed like a paycheck.

So the more successful the company becomes, the more brutal each vesting date gets. And he hasn't sold a single share — the company is still private — so no money is coming in to cover any of it. He owes real tax, in cash, on paper gains he cannot touch.

The Election

The 83(b) election flips the timing.

Within 30 days of buying the shares, Surya can file a single page telling the IRS to tax him now, at exercise, as if the shares were already fully vested. At exercise, each share is worth what he paid for it, so the gap the IRS taxes is $0. He pays nothing.

That one move does two things. It locks in his tax bill while the shares are still cheap, and it starts his capital gains clock immediately, so every dollar the shares gain from here is the good kind of gain, taxed low and only when he actually sells.

The catch is the calendar. The window is 30 days from the purchase, and there are no extensions. A postmark on day 31 is worth exactly as much as never filing at all.

The Fork

Say the company does what everyone hoped. The price investors pay climbs from pennies to $200 a share over four years. Surya's 100,000 shares vest evenly, 25,000 a year.

Down one path he filed the election in month one. Down the other he forgot. Same shares, same company, same climb.

The path where he forgot owes nearly $4.7M in ordinary income tax, spread across four years, every dollar due in cash on stock he still can't sell. The filed path is a single line: $0 at exercise, then nothing until he actually sells, taxed at the lower capital gains rate. His $0.50 strike is so small it barely dents the bill either way.

The Window

What makes the 83(b) so cruel is that it never announces itself.

You don't get a bill for skipping it. You don't get a warning. The election simply lapses on day 31, quietly, and the consequences arrive years later disguised as a normal vesting event. By the time the tax shows up, the window closed so long ago that most people never connect the two.

Every other equity mistake gives you room to recover. A bad exercise timing, a concentrated position, a missed deduction, there is usually a next move. This one has no next move. The IRS does not accept late elections, does not care that you never heard of it, and does not reopen the door.

The same logic reaches anyone holding shares before they've vested. A founder buying restricted stock at incorporation, an employee early-exercising options, all of them face the identical 30-day window and the identical permanence. (Incentive stock options add their own wrinkle, the alternative minimum tax, but the deadline is the same.)

The Move

Equity paperwork is usually the lawyer's problem, a stack of documents you sign once and file away. For almost everything, that works fine.

The 83(b) is the exception. It is the rare place where doing nothing is the expensive choice, and where a single page, mailed in the first month, is the cheapest insurance in the tax code. The whole decision lives in a window that closes before the shares are worth defending.

If you're about to exercise options early, or you hold any stock that hasn't fully vested, the two paths are worth running before the clock starts, not after it stops. That's the kind of thing worth talking through while there's still time to act.

With stock you buy before it vests, the tax isn't a bill that arrives later. It's a decision you make in the first 30 days.

File it while it's cheap.