Co-founder agreement, what to include before you start building
Equity, vesting, IP, decisions, what a co-founder agreement must cover before you write the first line of code.
Do you need a co-founder agreement if you're friends?
Yes, especially then. A co-founder agreement covers equity, vesting, intellectual property, and decision-making. Without it, a breakup after a year can cost months of lawyers and zero trust.
Y Combinator publishes free templates. In Poland, consult a startup lawyer (e.g., when registering an sp. z o.o.).
What must a co-founder agreement include?
| Element | Why it matters |
|---|---|
| Equity split | Who owns what and why, in writing |
| Vesting (4 years, 1-year cliff) | Protection against leaving with full shares |
| IP assignment | Code, ideas, domains belong to the company |
| Roles and responsibilities | Who decides on product, sales, finance |
| Decision-making | Unanimous, majority, or veto on key matters |
| Exit terms | What happens when someone leaves (buyback, good/bad leaver) |
| Non-compete / NDA | Protection against competition and leaks |
How to split equity fairly?
There's no single formula, but fairness > math:
- 50/50, when both start from zero with equal commitment.
- 60/40 or 70/30, when one brings idea + customers + funding, the other technology.
- Slicing Pie, dynamic split based on time contribution (rare in Poland, popular in US).
Key: write the reasoning, "40% for CTO because they build the product from scratch, 4-year vesting", not "because I feel like it."
Vesting, how does it work in practice?
Example: 40% shares, 4-year vesting, 1-year cliff.
- After 12 months, you earn 10% (1/4 of the package).
- After 24 months, 20%.
- After 48 months, full 40%.
If you leave after 6 months, 0%. This protects remaining co-founders.
IP, who owns the code?
Everything you create within the startup should belong to the company, not individual founders. An IP assignment agreement is standard. Without it, a departing CTO can take the code.
When to sign the agreement?
Before you write the first line of code together, not "when there's traction." The earlier, the easier an honest conversation. After the first customer, emotions and stakes grow.
Where to find templates?
- Y Combinator, Safe and co-founder agreement templates
- Stripe Atlas, documents for US companies
- Polish startup lawyers, adaptation for sp. z o.o. and KSH
Summary
A co-founder agreement is the best hour of your founding year. Equity, vesting, IP, and decisions, written upfront saves months of conflict.
Before you search for a partner, Foundersi helps you find someone with real building intent. When you find them, agreement first, then code.
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