Two founders start a limited company, split the shares fifty-fifty, and agree everything else will 'sort itself out' as they go. It usually does — right up until one of them wants to leave, or disagrees with the other about the business's direction, or stops pulling their weight, and there's no document anywhere that says what happens next. A shareholders' agreement is the document that answers those questions while everyone's still getting on, so nobody has to negotiate them for the first time in the middle of a falling-out.
What it actually is
A shareholders' agreement is a private contract between the shareholders of a company, sitting alongside the company's articles of association at Companies House. Where the articles are a fairly generic legal framework, the shareholders' agreement is where the specific, honest arrangement between the actual people involved gets written down — who decides what, what happens if someone wants out, and what happens if things go wrong. It isn't legally required to start a company, which is exactly why so many founders skip it, and exactly why so many later wish they hadn't.
Decision rights: who actually has to agree
The most practical clause in most agreements is a list of decisions that need unanimous or majority shareholder agreement, rather than being left to whoever happens to be running day-to-day operations. Taking on debt above a certain amount, issuing new shares, changing the company's core business, or paying out dividends are common ones. Without this, a majority shareholder can technically make sweeping decisions alone — which might be exactly what you intend, or might be the opposite of what a minority co-founder assumed when they signed up.
Leaver provisions: the clause everyone skips and everyone needs
This is the one that saves relationships. What happens to someone's shares if they leave — whether by choice, by being pushed out, or through illness or death? Good leaver and bad leaver clauses set different terms depending on the circumstances: someone who leaves on good terms after years of contribution is usually treated more generously than someone who leaves early or is removed for cause. Without this written down, a departing co-founder can simply keep their shares indefinitely, meaning the people still doing the work are permanently sharing profit and decision-making with someone no longer involved.
The people who most need a shareholders' agreement are the ones who are certain they'll never need it. That certainty is exactly the moment to get it in writing — not after the friendship has already started to strain.
Vesting: the clause most UK founders have never heard of
Common in venture-backed businesses and increasingly sensible for any multi-founder company: shares are earned over time — commonly across three or four years — rather than handed over in full on day one. If a co-founder walks away after six months, vesting means they leave with a fair slice of what they actually contributed, not an equal permanent stake earned in a fraction of the time everyone else stays. It feels unnecessary when everyone's excited and committed. It's precisely the clause that protects everyone if that changes.
Deadlock: what happens when two equal partners disagree
A fifty-fifty split feels fair at the start and can become a genuine problem the moment the two shareholders disagree on something significant, because neither side can outvote the other. A deadlock clause sets out what happens next — anything from a casting vote for a specific role, to mediation, to a mechanism for one side to buy the other out at a fair valuation. Deciding this in advance, while both sides are reasonable, is far easier than negotiating it in the middle of an actual disagreement.
Drag-along and tag-along: the clauses that matter when you sell
These two rarely get discussed early on, but they decide how a future sale actually plays out. A drag-along clause lets a majority of shareholders force a minority to sell on the same terms, if the majority agrees to sell the whole company — without it, a single small shareholder can technically block a sale everyone else wants, simply by refusing to sign. A tag-along clause protects the reverse case: if a majority shareholder sells their stake, a minority shareholder can insist on selling theirs on the same terms, rather than being left holding shares in a company under new ownership they never agreed to. Neither clause matters at all until the day someone actually wants to sell — at which point, whichever one is missing becomes the single most expensive omission in the whole document.
Picture two founders, sixty-forty, three years in. The sixty-percent founder gets an acquisition offer for the whole business. The forty-percent founder isn't ready to sell, doesn't want to work for the acquirer, and — with no drag-along clause in place — is legally entitled to simply say no, and hold the shares regardless of what the majority wants. The deal doesn't have to collapse, but it now involves solicitors, a renegotiation, and months of delay a five-minute clause agreed three years earlier would have avoided entirely. Nobody in that founding conversation was being difficult or short-sighted; they simply never got round to the document, on the reasonable assumption they'd sort it out if it ever came up. It came up.
What happens without one
Without a shareholders' agreement, disputes default to the company's articles of association and general company law — which are built for the general case, not your specific business or relationship. That usually means slower, more expensive, more adversarial resolution, often via solicitors and sometimes via court, at exactly the point when the business itself needs steady leadership most. It's the legal equivalent of not having anything in writing with your co-founder — a topic our piece on the agreement we never wrote covers from the other side of the same lesson.
Getting it done properly
A shareholders' agreement isn't a DIY template job for anything beyond the simplest structure — get a solicitor to draft or at least review one, because the clauses that matter most are precisely the ones that are easy to get subtly wrong. Expect a proper first agreement between two or three founders to be a modest, fixed-fee piece of work rather than an open-ended one, and treat it as cheap relative to what it's protecting — a small cost early on, against a very expensive one to sort out later. The best time to have this document is when nobody thinks they need it yet. That's also, unhelpfully, the exact moment it's easiest to skip.
Common questions
Do we really need one if it is just me and my best mate, 50/50?
Yes, and the closer the friendship the more it matters. A 50/50 split has no tie-break built into it: the moment you disagree on something needing a shareholder vote, neither of you can carry it and the company simply stalls. Company law offers no tidy default for that — the fallback is an unfair prejudice petition under section 994 of the Companies Act 2006, or a just-and-equitable winding-up petition, both of which mean solicitors, months of delay, and a business being run by two people who are suing each other. A deadlock clause agreed while you still like each other costs an afternoon. Agreed after the argument starts, it costs whatever the other side can extract.
Can I use a template, or does it have to be a solicitor?
A template can work for the simplest case — two founders, equal shares, no outside money, no employees holding equity. Anything beyond that earns a solicitor, because the clauses that matter most are exactly the ones that fail quietly when the wording is slightly off: leaver provisions, vesting, drag-along and tag-along, and the list of decisions requiring unanimous consent. You discover the defect years later, at the worst possible moment. Ask for a fixed fee and you will usually get one for a straightforward founder agreement. Whichever route you take, check the agreement sits consistently with your articles of association, because conflicts between the two are where disputes start.
What happens to a shareholder's shares if they die?
They pass under the deceased's will or the intestacy rules, which typically means they land with a spouse or children who have no involvement in the business and no wish to run it. The standard fix is a cross-option agreement: the surviving shareholders hold an option to buy and the estate holds an option to sell, funded by life cover written into trust so the cash actually exists on the day. The drafting matters — a binding obligation to buy and sell can jeopardise Business Property Relief, whereas reciprocal options generally do not. From 6 April 2026 business relief covers the first £2.5 million of qualifying assets at 100%, with 50% relief above that.
Can I force out a co-founder who has stopped pulling their weight?
Not without a mechanism you agreed in advance. A shareholding is a property right: you cannot cancel it because someone stopped contributing, and while a director can be removed from the board by ordinary resolution, they keep every share they hold on the way out. That gap is exactly what leaver provisions and vesting exist to fill — they settle, before anyone falls out, what a departing shareholder's stake converts to and at what valuation. Without them your options are to negotiate a buyout at whatever price they will accept, or to argue unfair prejudice under section 994, which is slow, expensive and unpredictable. The clause is cheap; the alternative is not.
We have been trading for years without one. Is it too late?
No. The right time is whenever you notice you do not have one, and year seven counts. Nothing about an established company stops the shareholders signing an agreement now: it is a private contract between them, never filed at Companies House, so there is no public record and no filing deadline to miss. The thing that genuinely gets harder with time is agreement itself, because contributions have diverged and leaver terms are no longer an abstract conversation. If shares change hands while you tidy things up, remember stamp duty at 0.5% on transfers where the consideration is over £1,000, paid by the buyer via the stock transfer form.
