Designing Co-Founder Vesting — A Practical Guide to Cliffs, Acceleration, and Clawbacks

#Why It's Dangerous Not to Have a Vesting Clause

The moment a co-founder signs the paperwork, they become a shareholder as a matter of law. Without a separate vesting condition, their equity stays put even if they leave a week later. In every subsequent funding round, investors factor that departed shareholder's stake straight into their math. The result: the team still working gets a smaller slice than it should.

Vesting is a structure that has you earn your equity gradually, in proportion to how long you've contributed to the company — “equity earned in proportion to work done.” Conversely, if someone leaves, the company or the other founders can buy back whatever hasn't vested yet. That buyback right is what's known as a clawback.

The Silicon Valley standard is four-year vesting with a one-year cliff. Not many early-stage Korean startups have this structure properly in place yet. The most common mistake is fully vesting all equity on day one of incorporation. That mistake tends to surface either when the first investor review flags it, or only after a dispute has already broken out.

#The Basic Structure of Vesting — Cliffs, Monthly Vesting, and Acceleration

Vesting design rests on three axes: the vesting period (how many years total), the cliff (minimum tenure required), and acceleration terms (early vesting triggered by an M&A or termination). These three axes need to be combined and spelled out explicitly in the contract.

A cliff is the minimum condition that “equity only starts vesting once you've stayed at least this long.” With a one-year cliff, someone who leaves on day 364 has zero vested equity. The moment they hit the one-year mark, 25% (on a 4-year schedule) vests all at once, and after that, an additional slice vests every month. Without a cliff, someone who leaves after just three months still walks away with some vested equity.

Acceleration terms are a founder-protection mechanism. They prevent a scenario where a founder gets force-terminated right after the company is acquired in an M&A. Single-trigger acceleration (vesting accelerates on the M&A closing alone) is a heavy burden from the acquirer's perspective. Double-trigger acceleration (vesting accelerates only once both the M&A and a termination without cause occur) causes less friction in negotiations and is more commonly adopted in practice.

#Designing the Equity Clawback on Departure — Buyback Price and Method

If vesting is about “how much equity gets confirmed,” a clawback is about “how you get back the equity that never vested.” In Korea, this is often written into contracts as a “share buyback right” or a “right of first refusal.” The substance matters more than the label.

Buyback price is the crux of the negotiation. The three most common benchmarks are par value, original acquisition cost, and fair market value (FMV). Early in a company's life, since the real value of the stock is low, par-value or cost-basis pricing is typical. FMV-based pricing becomes more common after Series A.

The Good Leaver / Bad Leaver distinction is where disputes flare up most often in practice. A Good Leaver departs for health reasons, by mutual agreement, or for other legitimate cause. A Bad Leaver is someone who, for example, jumps to a competitor, breaches a material obligation, or commits embezzlement. Applying different buyback prices and ratios depending on the reason for departure — even for what looks like the same departure — prevents a substantial share of disputes.

The buyback procedure itself also needs to be spelled out in the contract. Without concrete language covering the notice period (e.g., exercise notice within 30 days of confirming departure), who has the right to buy (the company or the other co-founders), and when payment is due, the clause can end up toothless in an actual dispute.

#What to Confirm Before Drafting the Contract

The checklist below can be used whether you're drafting a new co-founder agreement or reviewing an existing one. Every item needs to be spelled out in the contract itself to hold up in a dispute.

1. Is the total vesting period stated in the contract in years (e.g., 36 months or 48 months)?
2. Are the cliff period and the vesting percentage triggered at the cliff stated as specific numbers?
3. Is the post-cliff vesting method (monthly or quarterly) clearly defined?
4. Is the acceleration trigger (M&A/termination) specified as single-trigger or double-trigger?
5. Is it specified whether the company or the co-founders hold the right to claw back unvested equity on departure?
6. Are the definitions of Good Leaver and Bad Leaver written out with enumerated examples?
7. Is the buyback-price basis (par value, cost, or FMV) specified by stage?
8. Are the notice period for exercising the buyback right and the payment schedule stated in numbers?
9. Is the governing law and jurisdiction specified in case of a dispute?
10. Has a legal professional (attorney) reviewed the agreement after it was drafted?

Meeting 7 or more of these 10 items means you have a basic protective structure in place. Fewer than 5, and you need to revisit the contract right now. Disputes only surface after a departure actually happens, but the damage is already baked in by how well the contract was designed at signing.

#5 Common Mistakes

There's a recurring pattern in how early-stage Korean founding teams get vesting design wrong. The items below are drawn from patterns that come up frequently in startup legal practice. Always confirm your specific contract with a professional.

1. Fully vesting equity on day one: Finalizing the shareholder registry the moment the company is incorporated, with no vesting clause at all. If someone leaves later, there's no legal basis to claw anything back.
2. Relying on a verbal agreement only: “Let's sort it out together if something comes up later.” Verbal agreements are hard to prove in a dispute, and courts rule based on the written contract.
3. Monthly vesting with no cliff: Someone who leaves after one month of work still walks away with 1/48th of their equity vested. Someone who leaves within a few months can end up with a meaningful stake.
4. Missing a buyback-price clause: You have the right to claw back unvested equity, but no pricing basis. If negotiations break down, the buyback right becomes toothless.
5. Giving up founder protection by skipping acceleration terms: If an acquirer terminates the founder immediately after an M&A, the founder loses their unvested equity. A double-trigger acceleration clause is recommended as a minimum founder-protection mechanism.

Each of these five mistakes looks minor in isolation. But when a co-founder departure actually happens, they become variables that can shake the company's very survival. A contract isn't something you write while the team is running smoothly — it's something you write in advance, in case the team goes bad.

#Frequently Asked Questions

Q. We've already incorporated — can we still add a vesting clause now? — Yes, you can. You can add it by drafting a shareholders' agreement (SHA) or amending your existing agreement. That said, it requires the consent of all shareholders, and if a lot of time has passed since incorporation, you may need structural adjustments like retiring a portion of existing shares or reallocating new shares.

Q. If we raise investment during the vesting period and get diluted, does the vesting ratio change too? — Generally, the vesting clause itself doesn't account for dilution from fundraising. The vesting schedule runs against the original agreed-upon share count, not against the founder's equity percentage. Even if the equity percentage changes after a raise, the vesting schedule stays as originally set.

Q. If someone leaves after passing the cliff, is already-vested equity completely unrecoverable? — In principle, already-vested equity isn't subject to clawback. That said, you can address this through a Bad Leaver clause that grants a right of first refusal (a forced sale at a specified price) even over vested equity. This, too, only has effect if it's spelled out in the contract in advance.

Q. Are stock options different from vesting? — Yes. Vesting is the condition under which already-granted shares become earned. A stock option is the right to buy shares at a specific price in the future. Options often carry their own vesting schedule too, but the legal structure differs from co-founder equity design. It's common to structure co-founders' equity through vesting and early employees' equity through stock options.