Among the many things a new founder is told to handle, the 83(b) election is the one with the shortest fuse and the least forgiveness. It is a single-page filing with a hard 30-day deadline, and missing it is one of the more expensive avoidable mistakes in startup life.
When you receive equity that vests over time, the default tax treatment can tax you as it vests, on the value at each vesting date, which for a company that is growing can mean a rising tax bill on stock you cannot yet sell. An 83(b) election tells the IRS you would rather be taxed now, on the value today, which for early-stage equity is often very low. You are choosing to recognize a small amount now instead of a potentially large amount later.
The election must be filed with the IRS within 30 days of receiving the equity, and the deadline is famously unforgiving, with no general extension. Founders miss it because the window opens at the busiest, most chaotic moment of a company's life, and because nobody is assigned to watch it. The cost of missing it is not theoretical; it can convert a trivial tax event into a significant one as the company appreciates.
An 83(b) election is not automatically right; it involves paying some tax now on equity that could, in principle, become worthless. It tends to favor situations where the current value is very low and the upside is large, which describes a lot of early founder equity, but the decision depends on the numbers and your circumstances. Because the window is so short and the stakes so high, this is a conversation to have with your tax advisor the moment equity is on the table, not a month later. This is general information, not personalized tax or legal advice.
One form, thirty days. Do not let the clock decide for you.