Two friends started a business together on a handshake and a rough 50/50 understanding, because writing anything formal felt like planning for a divorce before the wedding. For the first eighteen months it didn't matter — the business was small, the roles were obvious, and any friction got sorted over a pint. Then the business started genuinely working, a third person wanted to buy in, and it became clear that nobody actually knew, in writing, who owned what, who decided what, or what happened if one of them wanted out. That gap nearly ended both the friendship and the company.
Why it felt unnecessary at the start
When you start a business with a friend, a written agreement feels almost insulting — as if you're planning for the relationship to fail before it's begun. Everything's informal because everything's obvious: you built it together, you split things fairly, you trust each other completely. That trust is real and it's also exactly why nobody stops to write it down. The problem isn't the trust. It's that 'fair' means something different to each person the moment real money or real decisions are on the table, and nobody discovers the gap until it matters.
Where it actually broke
The moment it broke wasn't dramatic. An investor offer came in, and the two founders discovered they'd never actually agreed what 'roughly 50/50' meant in practice — one had assumed it accounted for the extra hours he'd put in during the first year when the other had kept a day job; the other assumed a clean, equal split regardless of history because that's what they'd shaken hands on. Neither was being dishonest. They simply had two different memories of an agreement that had never been written down, and no document to settle which one was right. The conversation that followed was the worst either of them had ever had, and it happened at the exact moment the business needed them working together most.
A handshake agreement isn't really an agreement. It's two people's separate memories of a conversation, which quietly diverge over time without either person noticing until money is on the table.
What a proper agreement should have covered
Looking back, the document that should have existed on day one didn't need to be complicated — it needed to cover four things clearly. Who owns what percentage, and on what basis if that ever changes (does someone earn more equity for extra hours, or does it stay fixed regardless of who does what week to week). How decisions get made, especially the ones that matter — spending above a certain amount, taking on debt, bringing in outside investment — and what happens if the two of you disagree. What happens if one person wants to leave, is forced to leave, or simply stops contributing what was expected, including how their share gets valued and bought out. And what happens if the business is sold, including whether both founders need to agree or a majority can force a sale.
The conversation is harder than the document
The document itself is the easy part — a solicitor can draft co-founder terms in a few pages once you know what you actually want it to say. The hard part is the conversation that has to happen first: sitting down while everything's still friendly and forcing yourselves to talk through the scenarios where it wouldn't be — what if one of us wants out in two years, what if we disagree about taking on investment, what if one of us just stops pulling their weight. Those conversations feel unnecessary and slightly paranoid when the business is small and the friendship is strong. They're dramatically easier to have then than after the disagreement has already started.
Why it matters more, not less, between friends
The instinct is that a written agreement is for business partners who don't fully trust each other, and unnecessary between friends. It's almost the opposite. Strangers going into business together tend to negotiate terms cautiously from the start, precisely because they don't assume goodwill will cover every gap. Friends assume the goodwill will always be enough, which is exactly what makes the eventual disagreement so much more painful — it doesn't just cost money, it costs the friendship the business was partly built to protect in the first place.
What we did once it nearly went wrong
The agreement eventually got written, after the argument rather than before it, which is a worse time to write one — trust had taken a real hit, and negotiating equity terms while still annoyed with each other is much harder than negotiating them as a formality on day one. It held the business together, but a version of that document written eighteen months earlier would have prevented the argument entirely rather than just resolving it. That's the real lesson: the agreement isn't there for when things go wrong. It's there so the version of the conversation that happens when things go wrong is 'let's check what we agreed' rather than 'let's work out, right now, under pressure, what we think we agreed'.
What we'd tell anyone starting out with a friend
If you're starting a business with someone you trust completely, that trust is exactly why it's worth writing the agreement — not despite it. Get proper terms drafted before any money changes hands or any real decisions get made, cover equity, decision-making, and what happens if someone leaves, and treat the conversation as a normal part of setting up a business rather than a sign the partnership is fragile. It isn't a vote of no confidence in the friendship. Done early and calmly, it's one of the things most likely to keep both the business and the friendship intact.
Common questions
Isn't a 50/50 split fine if we both own half the company?
A clean 50/50 split with nothing else written down is the most deadlock-prone structure there is. Owning half each means neither of you can pass an ordinary resolution without the other, so a genuine disagreement about strategy, spending or taking investment simply stops the company dead. There is no tiebreak and no way to force a resolution short of one founder leaving or a court winding the company up on just and equitable grounds. Equal ownership is perfectly fine — but write in a deadlock mechanism alongside it: an independent chair with a casting vote, a mediation step, or a shoot-out clause where one founder names a price and the other chooses to buy or sell at it.
What is vesting, and should co-founders have it?
Vesting means a founder earns their shares over time instead of owning them outright on day one, and yes, most co-founder teams should have it. The common structure is four years with a one-year cliff: leave inside twelve months and you keep nothing, after which the remaining shares vest monthly. It exists to prevent the single worst co-founder outcome — one person walking away after six months still holding half the company while the other spends a decade building it. Mechanically it is usually a reverse vesting clause letting the company buy back unvested shares at nominal value. Any professional investor will expect it, so agreeing it early avoids a bruising renegotiation at the first round.
Do we need a shareholders' agreement, or will the articles do?
Realistically both, because they do different jobs. The articles of association are the company's public constitution, filed at Companies House and readable by anyone; most companies adopt the Model Articles, which say almost nothing about how founders deal with each other. A shareholders' agreement is a private contract between the founders covering equity splits, vesting, decision thresholds, what happens when someone leaves and how a sale gets approved. Provisions that need legal effect against the outside world — share transfer restrictions, drag-along and tag-along rights — usually have to sit in the articles too, so the documents get drafted together. Budget for a solicitor; template packs rarely handle leaver terms properly.
What happens if one co-founder just stops turning up?
Without an agreement, very little — which is precisely the problem. They remain a shareholder, keep their full percentage, keep any share of a future sale, and if they are also a director they keep those powers until formally removed by shareholder resolution, which needs votes you may not have. A shareholders' agreement solves this with good leaver and bad leaver provisions: a good leaver, someone going for health or other agreed reasons, keeps vested shares and is bought out at fair value; a bad leaver, someone who walks or is dismissed for cause, sells at nominal value or a discount. Define both categories precisely, because arguing over which applies is where these disputes actually land.
We've been going two years already. Is it too late to write one?
No, and late is still far better than never — but do it before the next thing that raises the stakes, not after. Negotiating terms while the business is stable and both founders feel fairly treated is materially easier than negotiating them during an investment round, an acquisition approach or a falling-out. Start with what you both already believe is true: current ownership percentages, who decides what, and what a fair exit looks like for each of you. Where you disagree, that disagreement already exists — the document is simply the first time you have both seen it. Expect vesting to be the hardest conversation, since applying it retrospectively means agreeing some shares are not yet fully earned.
