83(b) Election
A filing that lets a founder pay tax on restricted shares at grant, when they are worth almost nothing, rather than as they vest.
An 83(b) election tells the US tax authorities you want to be taxed on restricted stock at the moment it is granted rather than as it vests. At founding, when shares are worth fractions of a cent, that tax is negligible.
Without it, you are taxed on the value of each tranche as it vests. If the company appreciates sharply, a founder can face a large tax bill on shares they cannot sell.
The election must be filed within 30 days of the grant. The deadline is absolute — there is no extension and no remedy for missing it, which makes it one of the most consequential pieces of paperwork in a company's first month.