The Thirty-Day Window: Do I need to file an 83(b) election?

There is a one-page form you have exactly 30 days to file with 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

Linda is employee number twelve at a young startup. Her offer includes a grant of 100,000 stock options at a strike price of $0.50, the price she 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 Linda's company, like many, lets employees exercise early, buying the shares before they vest.

So Linda writes a check for $50,000 and buys all 100,000 shares up front. The shares are hers, but they are restricted until they vest. The company can buy them back for what she paid if she 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 hers 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 Linda does nothing after exercising.

The IRS waits. It taxes each block of shares the moment it vests — not when she bought it — on the gap between her $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 her 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 she hasn't sold a single share — the company is still private — so no money is coming in to cover any of it. She owes real tax, in cash, on paper gains she cannot touch.

The Election

The 83(b) election flips the timing.

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

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

The filing itself finally caught up with the stakes. For decades this meant certified mail and a prayer for the postmark. The IRS now runs an online portal, so the election can be filed electronically in minutes. Two copies matter: the IRS gets the election, and your company gets a copy, which the rules require.

The catch is the calendar. The window is 30 days from the purchase, and there are no extensions. 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. Linda's 100,000 shares vest evenly, 25,000 a year.

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

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

The Sale

That $4.7M deserves an honest footnote: it is not the lifetime price of forgetting. It is the cash the IRS collects during the vesting years. Eventually, on either path, Linda sells, and the sale triggers capital gains tax for both versions of her.

Here the forgotten path gets its one consolation. The tax paid at each vesting date bought her basis. The IRS doesn't tax the same gain twice, so the $8.75M that vested across those four years, already taxed as income, is subtracted at the sale. The filed path, which has paid nothing yet, owes capital gains on the entire climb.

Say she sells all 100,000 shares at $200, a $20 million exit.

The true lifetime gap is about $1.5M, and it comes from the rate. The same vest-date growth is taxed north of 50% as ordinary income on one path, and around 37% as long-term capital gains on the other, stacking the 20% federal rate, the 3.8% net investment income tax, and state on top.

But the rate is only half the story. Look at when the money leaves. Without the election, $4.73M walks out the door across the vesting years, in cash, on stock she cannot sell. With it, she keeps that $4.73M working for her and settles the entire bill on the one day the sale hands her $20 million to pay it with. The election doesn't just shrink the tax. It moves every dollar of it to the moment there's actually money on the table.

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, filed 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.