October 26, 2026
Split founder equity based on the work each founder will do from here on, not on who had the idea, and default to equal shares unless there's a clear reason not to. Whatever the split, put every founder on vesting, issue the stock when you incorporate, and file each founder's 83(b) election within 30 days.
Key takeaways
Splitting equity is hard because you're guessing. Nobody knows who will create the most value over the next several years, and the conversation happens just as everyone is making a big life decision. Useful factors include each founder's role and how central it is, relevant experience and skills, whether each founder is full-time, and what each person is giving up to do this.
Past contributions matter less than they feel like they do. Startups succeed on years of execution, not on the idea or the first few months of work. An idea alone is worth very little. Focus on who is essential to growing the company, and on keeping every founder fully committed to it.
Agree on the facts the split is supposed to reflect, then choose the numbers. Settle when each founder starts full-time, who will be CEO and which decisions that role owns, and what each founder is responsible for delivering over the next year. Talk about money: whether anyone is putting in cash or signing a personal guarantee, which should be handled outside the split, and whether anyone needs a salary sooner than the others. Be specific about prior work, such as code, designs or a prototype built before incorporation, and about outside commitments, such as a day job, a consulting practice or another startup, because both affect what the company owns and how much time it gets. Finally, agree on what happens if someone leaves, which for most teams means standard vesting and a vesting start date for each founder that matches when they actually began.
Once you've agreed, write a one-paragraph memo explaining why you chose the split, have every founder sign it, and keep it in the minute book. When a co-founder leaves or an investor asks about the split two years from now, a short record made at the time is worth more than everyone's memory. See How Do I Assign IP I Built Before Incorporating to My Startup?
Usually, yes, or close to it. Y Combinator has long recommended equal splits, and many experienced founders agree. Building a startup is a long commitment, so differences that look big at the start shrink over time, and an unequal split can create resentment that hurts the company long after the reasons are forgotten.
An unequal split makes sense when the founders' roles or commitments are genuinely different, for example, when one founder is full-time and another is keeping a day job. Have that conversation openly and early.
Yes, and not only at the board. Under Delaware law, the biggest stockholder decisions need a majority of the outstanding shares: amending the charter, including to authorize more shares for a new founder, a larger option pool or a financing, and approving a merger or a sale of substantially all the assets. With two founders at exactly 50% each, neither has a majority alone, so either one can block all of these. Directors are elected by a plurality of the votes, so an evenly split vote can leave the existing directors in place, and a two-founder board can't act at all on anything the two disagree about. If the stockholders deadlock and fail to elect directors, or a board deadlock is harming the business and the stockholders can't end it, any stockholder can ask the Delaware Court of Chancery to appoint a custodian, which is the outcome nobody wants.
An equal split is still often the right choice. Plan the tiebreak when you form the company, while you still agree. Common fixes are a third director both founders trust, or a tie-break process written into a stockholders' or voting agreement. Some teams use a slightly unequal split instead. See the two-founder deadlock section of How Do I Build an Early-Stage Startup Board? and What Do Stockholders in My Startup Need to Approve?
No. Keep the equity split about work, and paper the cash as an investment. A founder who puts money into the company should get a SAFE or a convertible note on the same terms an outside angel would get, or be repaid for documented expenses. Mixing cash and equity in the founder split is one of the most common sources of founder resentment, because the cash is a one-time contribution while the equity reflects years of work. See SAFE and Founders' Expenses Before Formation.
A founder who keeps a day job should usually get a smaller share, with the same vesting as everyone else. Another option is to treat the person as an advisor or early hire until they commit full-time, then grant founder-level equity at that point. Whatever you choose, have them sign a CIIAA so the company owns their work, and check that their current employer can't claim it. See Can I Start a Startup While I Still Have a Day Job?.
Dynamic models, such as Slicing Pie, can help founders negotiate before incorporation, but they aren't a cap table. On the incorporation date, freeze the percentages, issue restricted stock to each founder in those proportions, and put everyone on vesting, with each founder's vesting start date set to when they began full-time work if you've agreed to give credit for it. From then on, changes in contribution are handled through vesting and future grants, not by re-slicing.
Two or three is the common range. Beyond that, each founder's share gets small and decisions get slow.
Be deliberate about who gets the title. "Co-founder" has no legal meaning and gives no rights on its own. A founder's rights come from their stock purchase agreement, their vesting schedule and any board seat. But the title is permanent in practice: once you've called someone a co-founder to investors, the press or your team, they stay one, even if they leave in the first year.
If someone important joins later, or isn't ready to commit fully, an early-employee grant from the option pool is often the better tool. See How Do I Pick a Startup Co-founder?. If you're talking to a venture studio that wants co-founder equity, the same care applies.
Every founder should vest, even with an equal split. It's common for a founder to leave in the first year or two, and without vesting, a departed founder keeps a large stake that the remaining team has to build value for. Vesting protects the founders from each other, and investors will expect it.
The standard is four years with a one-year cliff, then monthly vesting. Founders buy their shares at par value under a restricted stock purchase agreement, and if a founder leaves, the company can buy back the unvested shares at the price paid, typically $0.00001 per share. Founders who worked for months before incorporating can get credit for it: the vesting commencement date in each stock purchase agreement can be set to when that founder actually started full-time, not the incorporation date. Some founders also negotiate double-trigger acceleration, which speeds up vesting if the company is sold and the founder is let go. Each founder files an 83(b) election with the IRS within 30 days of the date the shares are issued (on Form 15620, online or by mail), with no extensions.
Issue founder stock when you incorporate rather than waiting until you "figure out the split." Delay can raise the price founders must pay for their shares and complicate the 83(b). See Vesting Schedule, Single vs Double Trigger Acceleration, Restricted Stock Purchase Agreement and 83(b) Election.
Say three founders form a company with 10,000,000 authorized shares and an option pool of 1,000,000 shares. They issue 8,000,000 shares to the founders and leave 1,000,000 unissued for a future co-founder or key hire. Two founders are full-time and take 3,000,000 shares each. The third is keeping a day job for now and takes 2,000,000. All three vest over four years with a one-year cliff.
On a fully diluted basis (8,000,000 founder shares plus the 1,000,000-share pool, or 9,000,000 shares), the full-time founders each start with about 33% and the part-time founder with about 22%. If a seed round later sells 20% of the company, those become roughly 27% and 18%, before any increase to the option pool. See How Many Shares Should a Startup Have?.
Test it before you sign by running a departure through the four-year schedule with a one-year cliff, using the cap table above.
If one of the full-time founders leaves at month 9, before the cliff, none of their 3,000,000 shares has vested. The company buys all of them back for $30 at $0.00001 per share, and the founder leaves with nothing for nine months of work. If they leave at month 30, 30/48 of their shares have vested, or 1,875,000, and the company buys back the other 1,125,000 for $11.25. Fully diluted shares fall to 7,875,000, and the departed founder holds about 23.8% of the company, close to the part-time founder's 25.4%, while the remaining full-time founder holds 38.1%.
Ask each founder whether both outcomes feel fair. If the month 9 result feels too harsh for someone who worked for months before incorporating, give them credit through an earlier vesting start date. If the month 30 result feels too generous, change the split or the vesting now, while everyone still agrees, not after someone has left. See What Happens to a Co-Founder's Equity When They Leave?
If you'd like help setting up founder equity, see our startup incorporation service or contact us.
