Co-Founder Agreements: What Should Be in Yours Before You Split Equity

Why verbal equity splits fall apart

A 50/50 verbal split feels fair on day one. The problem is that it is a snapshot of a moment, and startups change fast. One founder goes full-time while the other keeps a job. One brings the idea; the other builds the product for two years. One loses interest after six months but still "owns half." Without a written agreement, that early handshake becomes a permanent claim on the company, no matter what happens next.

The founder breakup is one of the most common ways early companies die, not from competition, but from a co-founder who left early holding a large, unearned stake that scares off investors and demoralizes whoever stayed. A written agreement with the provisions below is what turns "we agreed to split it" into something that survives contact with reality.

Money makes it worse. The moment a company has real value, a term sheet, revenue, an acquisition offer, a vague early split becomes something people fight over, and memories conveniently diverge. An unequal contribution that felt fine when the company was worth nothing feels very different when it is worth millions. Writing the terms down while the company is still worth little is not a sign of distrust; it is one of the kindest things co-founders can do for their future selves, and for the friendship.

Vesting and the one-year cliff

Vesting is the single most important protection in a co-founder agreement. Instead of owning your shares outright on day one, you earn them over time, commonly four years, with a one-year "cliff." The cliff means you earn nothing until you have been around a full year; after that, shares vest gradually (often monthly). If a co-founder leaves in month three, they leave with nothing, and their shares return to the company.

This protects everyone who stays. Without vesting, a founder can walk away early and keep a huge stake for work they never did, the exact scenario that kills fundraising. Vesting should apply to all founders equally, including you. Consider what happens on a sale of the company too: acceleration provisions decide whether unvested shares vest early if the company is acquired.

• Standard shape: 4-year vesting, 1-year cliff, monthly thereafter, applied to every founder.
• Decide on acceleration (single- or double-trigger) so a sale does not leave your unvested equity behind.
• Put the vesting schedule in writing before shares are issued, not after a dispute starts.

IP assignment, the company must own what you build

This is the provision that surprises founders most, and the one investors and acquirers scrutinize hardest. Each founder must assign the intellectual property they create for the company, code, designs, brand, inventions, to the company itself. If the IP lives with individual founders rather than the entity, the company does not actually own its own product.

The danger case: a co-founder who wrote core code leaves on bad terms, and it turns out they never assigned that IP to the company. Now the business is built on something a former founder can claim. A clean, written IP assignment from every founder to the company closes that door. It also needs to handle pre-existing IP, anything a founder built before the company, by listing it and excluding it, so ownership is unambiguous.

Roles, decision rights, and deadlock

Spell out who does what and who decides what. Titles matter less than decision rights: which choices need unanimous agreement, which one founder can make alone, and who has the final say in their domain. Ambiguity here is where day-to-day friction builds into resentment.

With two equal founders, also plan for deadlock, what happens when you fundamentally disagree and neither can override the other. A deadlock provision (a tie-breaker mechanism, a mediator, or a defined process) sounds pessimistic to write on day one, but it is exactly the clause you will be grateful for on the day you need it. A company that cannot make a decision cannot move.

What happens when a co-founder leaves

Founders leave, voluntarily, or because the others ask them to. The agreement should define the difference between a "good leaver" and a "bad leaver," and what happens to equity in each case. Vesting handles the unearned portion; a buyback provision handles the vested portion, giving the company (or the remaining founders) the right to repurchase shares from a departing founder at a defined price.

Without a buyback, a departed founder can sit on the cap table indefinitely, contributing nothing while diluting the people doing the work. Decide the terms now: what triggers a buyback, how the price is set, and the timeline. Doing this while everyone is aligned is far easier than negotiating it in the middle of a breakup.

Founder non-compete and non-solicit

It is reasonable to agree that a departing founder will not immediately start a directly competing company using the team’s work, and will not poach the company’s employees. But keep the scope reasonable, enforceability of non-competes varies enormously by state, and several states (California most notably) will not enforce them against individuals at all.

Aim for restrictions that protect the company without trying to bar a former founder from their entire profession: a narrow definition of "competitor," a limited time period, and a focus on non-solicitation of employees and customers rather than a blanket ban on working in the field. An overbroad founder non-compete is both unfair and, in many states, unenforceable anyway.

Put it in writing early, and revisit it

The best time to write a co-founder agreement is at the very start, before there is anything to fight over. It is far easier to agree that vesting applies to everyone when no one has left yet, and to set a buyback price when no one is being bought out. Waiting until there is money or tension on the table turns a routine document into a negotiation between people who no longer fully trust each other.

The agreement is not a one-time event, either. Roles shift, contributions change, new founders or key hires join. Build in a habit of revisiting the arrangement at natural milestones, a fundraise, a major hire, a change in who is full-time, and update it deliberately rather than letting the written terms drift out of sync with reality. An agreement everyone has read and re-confirmed is worth far more than one signed once and forgotten in a drive.

The company paperwork has to say the same thing

A co-founder agreement does not stand alone. It works alongside the company’s formation documents, the incorporation or LLC paperwork, the equity issuance, and any shareholder or operating agreement, and they all need to say the same thing. If your co-founder agreement promises vesting but the shares were issued outright with no restriction, the document that controls is whichever was actually executed, and that mismatch is exactly what causes disputes later.

Make sure the equity is properly issued and documented, that IP assignments are signed by each founder, and that any elections tied to restricted stock are handled on time, some of these have strict deadlines with no do-overs. This is general information, not legal advice, but the theme is consistent: the protections only work if the underlying paperwork actually implements them. A founder still bound by a former employer’s IP or non-compete terms should surface that up front, too, before it turns up during due diligence.

Red flags recap

If your co-founder arrangement is still a verbal understanding, or a written one missing these pieces, treat that as the risk it is. The clauses below are the ones whose absence causes the most damage.

• No vesting, founders own their full stake on day one, so an early departure keeps unearned equity.
• No IP assignment, the company does not actually own the product its founders built.
• Unequal or missing IP assignment for pre-existing tools, leaving ownership ambiguous.
• No buyback right, so a departed founder stays on the cap table indefinitely.
• No decision rights or deadlock mechanism for a two-founder company.
• An overbroad founder non-compete that is likely unenforceable and needlessly hostile.
• A generic "founders agreement" that has never been read against your actual situation.