How to Split Equity Between Co-Founders: The Framework I Use Before Anyone Signs

Most founding teams decide their equity split in under an hour, before anyone has shipped anything or missed a payroll. It is the most expensive decision a company makes in its first year, made with the least information anyone will ever have. Here is the process I take founders through before anyone signs, and the clauses that matter more than the percentage itself.

The handshake split is the one that costs you

Noam Wasserman's research on founding teams found that 73% of teams split the equity within a month of founding. One month in, you do not know who will quit when a salaried offer arrives, who will close the first customer, or who will still be answering the phone in year three. You are pricing four years of risk on one week of evidence.

The damage shows up later: a dormant co-founder holding 40% while one person carries the company, a cap table no investor will fund, a deadlock that freezes a decision for six weeks. From the investor side of the table, the split is rarely the real problem. The absence of vesting and decision rights is.

Equity is not a trophy for what happened before the company existed. It is the price of the next four years of risk.

Price four contributions, not the friendship

Stop arguing in percentages. Allocate 100 points across four buckets, score each founder in each, then convert the totals to percentages. These are my default weights for a pre-revenue company where everyone is expected to go full-time.

• Full-time commitment and opportunity cost: 45 points. The biggest bucket, because it is the biggest risk. Score by when each person goes full-time and what salary they give up.
• Role criticality: 25 points. Who owns the function that kills the company if it fails in the next 18 months. In most B2B businesses that is distribution, not product.
• Idea, prior work and IP: 15 points. Capped deliberately. An idea with code, a filed patent or a waiting list scores at the top of this bucket. An idea alone scores near the bottom.
• Capital at risk: 15 points. Cash from a founder's own account, scored against a stated pre-money figure, not a feeling.

A worked example

Two founders. A goes full-time from day one and brought the prototype. B stays employed for six months, then joins full-time, and puts in the first 40,000 euros of working capital.

Commitment: A scores 30 of 45, B scores 15. Role criticality: A owns product, B owns sales, so 12 and 13. Idea and prior work: A takes 10 of 15, B takes 5 for the market research and the first ten customer conversations. Capital at risk: B takes all 15. Totals are A 52, B 48. Round to 55/45 or round to 50/50. Either is defensible, because you can now say what you are paying for.

The point is not the number. It is that the conversation happens while you still like each other, and the logic is written down somewhere you can return to.

Answer these seven questions before you open the spreadsheet

1. Who is full-time, from which date, at what salary once revenue allows one?
2. If one of us takes a job offer in month eight, what happens to their shares?
3. Is founder cash equity, or a loan repaid before any distribution? Write the number and the instrument.
4. Who holds the casting vote when we disagree, and on which decisions does neither of us get one without the other?
5. How much are we reserving now for the first five hires, so we are not diluting in a panic later?
6. Who legally owns the code, the brand and the domain today? If the answer is a personal account, fix it now.
7. What triggers a review of this agreement, and who is in the room for it?

If a prospective co-founder will not sit through those seven questions, you have learned more than their answers would have told you.

Vesting is the clause that makes any split survivable

Founder shares should sit on a reverse vesting schedule: you hold them from the start, and the company can buy back the unvested portion if you leave. Four years with a one-year cliff is the market standard. Carta's illustration is blunt: under a four-year schedule, a founder who leaves after one year can have 75% of their shares repurchased.

Three details decide whether your schedule is worth anything.

• Good leaver and bad leaver terms. Define each in writing. A co-founder who leaves for health reasons and one who joins a competitor should not be treated identically.
• Acceleration on a change of control. Single trigger accelerates on acquisition, double trigger needs the acquisition and the founder being removed. Double-trigger terms are often easier to align with a buyer, but treatment depends on the agreement and transaction.
• Credit for time served. If you have been building together for a year before you paper this, ask your lawyer whether the vesting commencement date can recognise that work. Record the actual signing and grant dates accurately; do not backdate signed documents.

Founder vesting is still skipped routinely outside the US. I see it across Europe and Africa, and the pattern repeats: the first serious investor imposes it at the term sheet stage, on worse terms than you would have chosen. Instruments vary by jurisdiction too, so employee equity in the UK is usually an EMI option scheme and in France a BSPCE plan, while founder buy-back mechanics follow local company law. Agree the commercial terms yourselves, then pay a local lawyer to draft them. That bill is smaller than buying out a dormant founder.

Model the dilution before you argue about the last five points

Most founder arguments are about percentage points future rounds will shrink anyway. Carta's Founder Ownership Report 2026 puts median collective founder ownership at roughly 56% after seed, 36% at Series A and 16.1% by Series C, with the employee pool at 12.1% at seed.

Run your argument through those numbers. A five point gap at incorporation, 55/45 instead of 50/50, is worth about 2.8 points of the company after seed and 0.8 points by Series C. A missing vesting clause can cost you 40% of the company, held by someone who stopped working. The gap you are shouting about is a rounding error next to the clause you forgot.

The split decides who owns the company. Vesting and decision rights decide who runs it. Most teams negotiate the first and inherit the second.

One more figure from that report: 36% of startups founded on Carta in 2025 were led by solo founders, up from 31% in 2024. That matters if you are being pressured into a partnership for the sake of having one. The realistic alternative to the wrong co-founder is not failure, it is a solo company with a clean cap table.

The failure modes I see most, and what to do instead

• Equal splits chosen to avoid the conversation. An even split can be right. It is wrong when nobody can explain why it is right.
• No vesting at all. Add reverse vesting now, while everyone still expects to stay. Agree the principle early and have the documents drafted correctly. A quick conversation is not a substitute for enforceable terms.
• Overpaying the idea. Ideas are cheap to hold and expensive to execute. Cap that bucket and pay for execution.
• Founder cash treated as free equity. Price it. Either it buys shares at a stated valuation or it is a loan with repayment terms. Vague money becomes a grievance.
• A clean 50/50 with no tie-break. Two equal holders and no casting vote is a company one bad week can freeze. Appoint a deciding voice per domain, or name an independent third party for genuine deadlock on reserved matters.
• No hiring reserve. Model a future option pool, for example 10% to 15% as a planning scenario, alongside your actual hiring needs. Agree how and when it will dilute founder holdings rather than treating one range as mandatory.

Put it on paper, then keep it investor-ready

Five records turn the conversation into a documented arrangement. The exact documents, tax treatment and approvals depend on your jurisdiction; use qualified local legal and tax advice.

1. A founders' agreement covering roles, time commitment, salary triggers, the split and the review mechanism.
2. IP assignment deeds moving code, designs, domains and trade marks from personal names into the company.
3. The vesting schedule, reflected in the share subscription documents and the articles, not just in an email.
4. A cap table that is a maintained file, not a reconstruction attempted the week an investor asks for it.
5. Decision rights, listing reserved matters that need both founders and the day-to-day calls that do not.

These are also the first things a serious investor asks for, so they belong in the folder from the start rather than assembled under pressure. I have written separately about why investor readiness is a data room problem, not a pitch problem, and the founders' paperwork is where that folder starts. I treat this as stewardship rather than admin: a cap table states who carries the risk and who shares the reward, and getting it honest early is a form of respect for the people building with you.

What to do this week

Book 90 minutes with your co-founder and one spreadsheet. Allocate the 100 points across the four buckets, score each other out loud, and write a one page memo recording the totals, the reasoning, the vesting schedule, the option pool reserve and the tie-break rule. Send it to a lawyer in your jurisdiction to be papered. If you cannot get through the 90 minutes, you have your answer about the partnership, and it is cheaper to learn that now than at your Series A.

More practical pieces for founders sit in the entrepreneurship archive, free and without gates.