The 83(b) deadline is 30 days. The hard part is knowing which 30th day.

An 83(b) election is the only tax filing most founders make where being one day late is fatal and unfixable. There is no extension, no reasonable-cause relief, and no amended-return path back. So the arithmetic deserves more care than it usually gets.

The rule itself is simple. The IRS's own Form 15620 states it: an 83(b) election must be filed no later than 30 days after the date the property was transferred. Count 30 calendar days from the transfer — not from the board consent, not from the offer letter — and that is your date.

When the 30th day is not the deadline

Section 7503 of the Internal Revenue Code says that when the last day for performing an act under the tax laws falls on a Saturday, Sunday, or a legal holiday, performing it on the next succeeding day that is not one of those is timely. Most people stop reading there and assume "legal holiday" means the federal holidays everyone knows.

It does not, quite. Section 7503 defines a legal holiday as a legal holiday in the District of Columbia. And the District's list of legal public holidays, set out in D.C. Code § 1-612.02, is the eleven federal holidays plus one more: District of Columbia Emancipation Day, April 16.

That single extra day is the one that catches software. If your thirtieth day lands on April 16 and the tool you used only knows federal holidays, it will hand you April 16 as your deadline when the true deadline is the next business day. Being told a date one day early is harmless. The problem is a tool that is confidently wrong in either direction on a deadline that cannot be cured — and the same D.C. Emancipation Day rule is why the April individual filing deadline itself shifts in some years.

The observance rules stack, too. A D.C. holiday falling on a Saturday is observed the preceding Friday; one falling on a Sunday is observed the following Monday. That means a holiday can be *observed in the previous calendar year* — when January 1 lands on a Saturday, New Year's Day is observed on December 31 of the year before. A 30th day that falls on that December 31 rolls.

It is a postmark, not a receipt

The other thing worth internalizing: this is a mailing deadline. Under the timely-mailing-is-timely-filing rule, an election postmarked by the due date is on time even if it reaches the IRS weeks later. This is why certified mail with a return receipt is the universal practice among people who have done this more than once — the receipt is the only evidence you will ever have, and 83(b) elections are famously hard to confirm after the fact.

Form 15620's instructions say to file with the IRS office where the person performing the services files their federal return, and to give a copy to the employer (and to the transferee, if different). Follow the current instructions on the form itself; that is the authoritative source and it changes more often than commentary does.

What the election is actually betting

The election trades certainty now for treatment later. You recognize income at the value on the transfer date instead of as the stock vests, which for founder stock bought at fair value is usually zero income and starts the capital-gains clock immediately. If the company grows, that is a large win. If the stock is later forfeited, you generally get no loss deduction for the compensation income you already recognized. It is a bet that the value at transfer is low — which is exactly why it is a day-one decision.

Whether the election makes sense for you is a conversation with your tax advisor. Once you have had it, the date should be mechanical. We built a free calculator that applies §7503 including the D.C. holidays: [unfoldcfo.com/free/83b-election-deadline](https://www.unfoldcfo.com/free/83b-election-deadline).

Sources. IRC § 83(b); IRS Form 15620 and its instructions (irs.gov); 26 U.S.C. § 7503; D.C. Code § 1-612.02 (legal public holidays, including Emancipation Day). General information, not tax advice — the current Form 15620 instructions govern where and how to file.