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. Enter your transfer date and get the exact postmark date — including the weekend and District of Columbia holiday rules that quietly move it. Free, no signup, nothing you type leaves your browser.
Date the stock was transferred
For founder stock this is usually the date the restricted stock purchase agreement was signed and the shares issued — not the date of the board consent authorizing it, if they differ.
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.
IRC §83(b) · IRS Form 15620 instructions · 26 U.S.C. §7503 · D.C. Code §1-612.02
More free tools: SEC deadline calendar, Form 8-K deadline helper, and the Delaware franchise tax calculator.