Splitting founder equity

Equity among co-founders is not a participation trophy and not a pure measure of who typed the most lines in month one. It is a multi-year incentive alignment problem: who stays, who leaves, who owns what when the company is worth something and when it is worth nothing. Handle it with clear percentages, vesting and written departure rules — or inherit a deadlock that kills the company faster than a competitor will.

This sits on top of incorporation: you need a Delaware C-corp and actual stock purchases before the percentages mean anything.

The big idea

There is no universally correct split. There are consistently bad ones.

Roughly equal splits (or close: 50/50, 40/40/20, 30/30/30/10) are common for teams that start together with comparable commitment. Investors often read a 90/10 split between two full-time co-founders as a red flag: either one person is about to be resentful, or the "co-founder" is actually an early employee mislabeled for recruiting.

Factors that do justify uneven splits, if everyone agrees in writing:

• One founder started 12+ months earlier and built the core product alone
• One founder brings a uniquely scarce asset (key patent, regulatory license, distribution)
• One founder is part-time by design for a defined period

Factors that usually should not dominate:

• Who had the idea first
• Who is older or more senior in title
• Who is better at negotiating in the room

Negotiate the split when everyone is optimistic and broke — not after the first term sheet. Re-opening founder percentages under investor pressure is how friendships end.

Walking through a delayed start

If A built for a year and B joins at incorporation, a flat 50/50 without acknowledging prior work often breeds bitterness. A cleaner pattern is slightly uneven common stock plus identical vesting clocks from the grant date, so B earns into ownership by staying.

When someone joins six months in as a "co-founder," avoid rewriting history by handing them half the company overnight with no cliff. Better: a meaningful grant that still vests over four years from their start date, possibly with a shorter cliff (for example six months) if they are taking real risk. The early founders' prior vesting clock should keep running — do not reset everyone to zero unless you intentionally want that reset.

Common mistakes

• Handshake percentages — no stock purchase, no ledger, no 83(b).
• 90/10 between two full-time founders without a written story investors believe.
• Revisiting the split after a SAFE closes — early investors underwrote the prior cap table.
• Advisor equity at founder-level percentages — use small advisor grants with short vesting instead.

Check yourself

Two people both quit their jobs on the same day and build full-time. One "had the idea" a year earlier. What split is the default?

Near-equal. The idea alone rarely justifies 90/10 once both are taking the same risk.

A third person joins at month six as a "co-founder." Should you reset everyone's vesting to zero?

Usually no. Grant them a four-year vest from their start date; keep the early founders' clocks running.

Key takeaways

• Prefer near-equal splits for true co-founders starting together; document any unevenness with reasons everyone accepts.
• Delayed starts justify a modest unevenness plus identical vesting clocks — not a permanent 90/10.
• Titles do not equal already-earned ownership.
• Do not recut founder percentages after money is in.

Further learning

Next, how those percentages are actually earned: reverse vesting.