Thirty days, no extensions, no second chance.
The 83(b) election is the rare tax deadline with no cure: miss it and your stock is taxed as it vests, permanently. Two rules decide the date, and most calculators get the second one wrong. Here they both are — and if you want the date worked out and the statement drafted, the tool is over here.
Rule one: thirty calendar days
Treas. Reg. §1.83-2(b) says the election shall be filed not later than 30 days after the date the property was transferred. Calendar days, counted from the transfer — not from board approval, not from the day you countersigned. There is no extension provision anywhere in the regulation, and there is no cure: if the day passes, section 83(a) simply governs instead and the stock is taxed as it vests, at whatever it is worth then.
Rule two: the April 16 trap
Section 7503 of the Internal Revenue Code says that when the last day for performing an act falls on a Saturday, Sunday, or a legal holiday, doing it on the next non-holiday weekday is timely. The catch is what “legal holiday” means: a legal holiday in the District of Columbia. The District's holiday list is the eleven federal ones plus D.C. Emancipation Day on April 16 — the same holiday that pushes the April filing deadline in some years. If your thirtieth day lands on April 16, it moves, and a calculator that only knows federal holidays will tell you a date one day early. Being early is safe; being told the wrong date because a tool rounded the rule is not.
One more thing worth internalizing: this is a mailing deadline. Under the timely-mailing rule your election is on time if it is postmarked by the due date, which is why certified mail with a receipt is the standard practice — that receipt is the only evidence you will have if the IRS has no record of it. And since 2016 you no longer attach a copy to your own return; T.D. 9779 removed that, and §1.83-2(g) records the date it took effect.
IRC §83(b) · Treas. Reg. §1.83-2 · IRS Form 15620 instructions · 26 U.S.C. §7503 · D.C. Code §1-612.02
The 83(b) election tool takes your transfer date and gives the exact postmark date, with the §7503 roll applied and the reason for it named. That part is free and needs no account. The drafted statement — the seven items Treas. Reg. §1.83-2(e) requires it to contain, the copies §1.83-2(d) requires you to furnish, and where each one goes — is part of Documents.
Other free tools: SEC deadline calendar, Form 8-K deadline helper, and the Delaware franchise tax calculator.