If you just incorporated, signed a stock purchase agreement or received founder shares that vest over time, the 83(b) election is the most time-sensitive piece of paperwork on your desk. Miss the window and you can lose a tax choice you cannot get back, so it belongs on your day-one admin list for any new company in Palo Alto, Sunnyvale or anywhere else, right next to opening a bank account.
The good news is that filing got easier. The IRS now offers an online version of Form 15620, its standard 83(b) election form, so you no longer have to rely only on certified mail. This guide covers the deadline, the online filing steps and the common mistakes first-time founders make. It is general information, so check your own situation with a tax professional or startup lawyer before you file.
What an 83(b) election is and why founders file one
As Baker Donelson explains, restricted stock is normally taxed as it vests, based on its value at each vesting point. An 83(b) election lets you recognize the income when you receive the shares instead, based on their fair market value at that time, and later growth is then measured from that starting value. If your shares are worth little when they are issued, the income you recognize up front is small, which is why so many founders file the election right after receiving their shares.
Your lawyer usually prepares the stock purchase documents, but the filing itself is your responsibility as the person receiving the shares. That can catch people off guard, especially second founders who join a few weeks after incorporation and assume someone else handled it. If you are still assembling your founding team, our guide on how to find a co-founder in the South Bay and Peninsula is a good companion read, because every new co-founder with vesting stock faces the same deadline.
The 30-day 83(b) deadline explained
The deadline is strict. A Baker Donelson client alert on the new online option, citing the tax code, says the election must be made no later than 30 days after the date the restricted property is transferred, and that late elections are not permitted. Goodwin's alert makes the same point, noting that there are generally no exceptions to the timing.
Count calendar days from the transfer date on your stock purchase agreement, then put a reminder at day 10 and day 20. Weekends and holidays do not pause the clock, and the Thanksgiving week is a classic place for a filing to slip. If you signed your documents in early November, check your date today.
How to file Form 15620 online with the IRS
According to Baker Donelson, the IRS released Form 15620 in late 2024 as a standardized form for 83(b) elections. Before that, founders typically drafted their own statements from templates. The IRS now lists Form 15620 on its mobile-friendly forms page, with a revision date of April 2025 and a posted date of June 29, 2025.
The IRS page lays out the basic process:
Sign in to an IRS Online Account, which is required for mobile-friendly forms that need a signature. The IRS says to add your work email to your ID.me account or create a Login.gov account if you are using the account for business purposes.
Fill in Form 15620 on the IRS website.
Choose to submit the form online or download a copy to mail.
Wait for the success message, which comes with a link to download your submitted form.
Goodwin's alert adds 2 practical points. Pick one method, either online or mail, and do not file the same election both ways; the form asks you to confirm you have not already mailed an election for the same equity. And after you submit online, give the downloaded copy to your employer or the company that issued the shares.
Common 83(b) mistakes Bay Area founders make
Most 83(b) problems come down to timing and record keeping. These are the ones worth guarding against:
Waiting for the lawyer to file it. Your counsel may remind you, but the election is yours to make.
Losing the proof. Save the IRS success message and the downloaded form with your incorporation documents, because investors or acquirers may ask to see it during diligence.
Skipping the company copy. Send the issuer a copy so your cap table records match.
Assuming the online form covers every structure. Goodwin notes that partnership interests or tiered ownership may need more detail than Form 15620 allows, so ask your advisor before using the standard form in those cases.
Clean paperwork pays off later. When you start fundraising, our guide on how to raise a Series A in 2026 covers what investors look for, and our post on product-market fit red flags for AI startups covers the metrics side.
Where to get founder advice in the South Bay
Paperwork questions are easier with a room full of people who have filed the same forms. Tribe organizes South Bay Renaissance to rebuild the startup and social scene of the South Bay and Peninsula in person, with founders' dinners, demo nights and talks from Redwood City to San Jose. It started with The First Gathering in Sunnyvale on Aug 28, and the calendar has grown since.
The next chance to compare notes is Tribe of Founders, an intimate monthly dinner in Sunnyvale on Nov 12, listed on the Tribe Events calendar. If you want to host something yourself, our guides on hosting a founder dinner in the Bay Area and hosting a startup demo night in the South Bay walk through the logistics. For a recent example of founders who did their homework before building, see our breakdown of Charta Health's $55M Series B.
Find your people before your next deadline
Founder admin feels lighter when you can ask a quick question and get an answer from someone a year ahead of you. The South Bay Renaissance group chat is where Peninsula and South Bay founders swap lawyer recommendations, filing tips and event invites. Follow the Tribe Events calendar on Luma to catch the next dinner, demo night or AI deep dive near you.
