Of all the decisions a founding team makes in the early days, equity is the one that follows you the longest. Get it right and it's invisible. Get it wrong and it becomes the fault line that everything else eventually breaks along.
The good news is that most equity mistakes are predictable. The same errors show up across founding teams at almost every stage, and almost all of them are avoidable with a structured conversation and the right documents in place early.
Here are the five we see most often.
Mistake 1: Splitting equally without actually thinking about it
A 50/50 split feels fair, so most co-founders default to it without much discussion. Sometimes it is fair. More often it's just the path of least resistance, and it papers over real differences in contribution that will surface later.
Equal splits only make sense when founders are genuinely contributing equally across experience, capital, network, and ongoing time commitment. If one person came up with the idea, has the deeper industry relationships, or is taking a bigger financial risk by leaving a higher-paying job, a strict 50/50 doesn't reflect reality.
A 55/45 or 60/40 split can feel uncomfortable to propose, but it often leads to a healthier dynamic than a split that both founders privately feel is wrong from the start. The conversation is hard. Have it anyway.
Mistake 2: Setting equity on day one with no vesting
This one gets its own full article on this blog, but it belongs on this list too because it's that important. Granting full equity upfront with no vesting schedule means a co-founder who leaves three months in walks away with whatever percentage you agreed to on day one. No mechanism to claw it back. No protection for the founders who stay.
The standard structure is four years of vesting with a one-year cliff. It's what investors expect, it's what protects the founding team, and it's one of the easier things to get right if you do it from the beginning.
Mistake 3: Not reserving an option pool
This is the mistake that tends to blindside founders at their first fundraise. If you've allocated 100% of equity between the founding team, there's nothing left for early employees, advisors, or the option pool that institutional investors will require before closing a round.
The result is that the option pool gets carved out after the term sheet, which means it comes out of the founders' shares rather than being priced into the pre-money valuation. It's a dilution hit that founders who planned ahead avoid entirely.
Reserve 10 to 20% of equity as an unallocated option pool before you go into your seed round. It's standard practice and investors will expect to see it.
Mistake 4: Ignoring what dilution actually looks like
Founders often anchor on their founding percentage without modeling what it looks like after a seed round, a Series A, and a Series B. A 40% stake today might be closer to 8% after two or three rounds of institutional capital. That's not necessarily a bad outcome, especially if the company is worth substantially more, but founders who haven't run those numbers tend to feel blindsided when they see them in a term sheet for the first time.
Build a basic cap table model early. Walk it through two or three hypothetical funding rounds with realistic dilution assumptions. Understanding what you're working toward makes every fundraising conversation easier.
Mistake 5: Not documenting informal equity promises
Early contributors often get equity promises that never make it into a formal document. An advisor who helped you get your first customer. A contractor who took below-market rates in exchange for a small stake. An angel who wired money before you had a SAFE in place.
These informal arrangements create real legal exposure. During due diligence, any undocumented equity claim becomes a problem, and resolving them under time pressure is both expensive and distracting.
Document every equity grant from day one, no matter how small. Use a SAFE for early investors. Use a formal advisor agreement for advisors. A one-page document signed by both parties is infinitely better than an email thread or a handshake.
The approach that actually works
The best equity structures are intentional, documented, and built with some acknowledgment that circumstances will change. Your co-founder agreement should formalize the split, include a vesting schedule, establish what happens when someone leaves under various scenarios, and define how future equity grants get approved.
None of this needs to be complicated. It just needs to be written down before anyone assumes otherwise.
This post is for informational purposes only and does not constitute legal advice. Consult a licensed attorney before making decisions about your equity structure.