Founders' agreement vs shareholders' agreement — what's the difference?
By SuLe · Updated 2 July 2026
A founders' agreement is the lightweight early document recording the deal between co-founders — roles, equity split, vesting, IP and commitment — while a shareholders' agreement is the fuller, binding company document governing share rights, leavers, transfers, drag-along and reserved matters. Most startups sign the first early, then supersede it with the second at incorporation or their first funding round.
Key facts
- A founders' agreement is signed by the founders personally, often before the company exists.
- A shareholders' agreement binds all shareholders — usually the company too — and covers share rights, leavers, drag and tag, reserved matters and transfers.
- The shareholders' agreement usually supersedes the founders' agreement through an entire-agreement clause.
- Vesting and buyback mechanics only gain teeth once implemented in the shareholders' agreement or articles.
- Neither document is filed at Companies House — unlike your articles of association, both stay private.
What does each document actually cover?
They answer different questions. The founders' agreement answers "what have we agreed between us?"; the shareholders' agreement answers "how does this company's ownership actually operate?".
| Founders' agreement | Shareholders' agreement | |
|---|---|---|
| When signed | Before or around incorporation | At incorporation, or at the first investment round |
| Parties | The founders personally | All shareholders, usually plus the company |
| Covers | Roles, equity split, intended vesting, IP, commitment | Share rights, vesting and leavers, transfers, drag and tag, reserved matters |
| Machinery | Light — a record of the deal | Wired into the company's articles and share mechanics |
| Lifespan | Until superseded — often within a year | Until replaced, typically at the next round |
| Public? | No — private | No — private (only the articles are public) |
Which one do we need first?
It depends where you are. Pre-incorporation with a co-founder, the founders' agreement is the only document you can sign — the company does not exist yet — and it captures the split, vesting intent and IP promises while goodwill is high.
Once incorporated, the balance shifts quickly. If shares have been issued and anyone might leave, the vesting and leaver machinery belongs in a shareholders' agreement and articles now, not at some future round.
If investors are already arriving, skip the founders' agreement entirely and go straight to the shareholders' agreement — papering the same deal twice helps nobody.
What happens to the founders' agreement when the SHA arrives?
It should be superseded — cleanly and expressly. A well-drafted shareholders' agreement includes an entire-agreement clause stating that it replaces earlier arrangements between the parties, so only one rulebook governs.
The handover is where value quietly leaks. The vesting start date agreed in the founders' agreement should carry across — if the new document restarts the clock at signing, founders silently lose months of vested equity.
Check consistency on everything else too: the split's logic, IP promises, commitment terms. Two documents that half-agree are a dispute waiting for its moment.
Why can't a founders' agreement just do the whole job?
Because the machinery it needs sits at company level. A contract signed before incorporation cannot bind a company that did not exist, and only the shareholders' agreement and articles — operating within the Companies Act 2006 framework — can deliver compulsory transfers, buybacks at nominal value, deferred-share conversions or transfer restrictions that actually stick.
Enforcement runs through the company's own records as well: the register of members is the legal record of ownership, and share transfers and allotments carry their own filings.
So the founders' agreement is the deal memo with evidential weight; the shareholders' agreement is the operating system. Startups with only the first have agreed what should happen without giving anyone the power to make it happen.
Worked example
Nell and Dominik sign a founders' agreement in January, before incorporating their GCSE revision app: a 65/35 split reflecting Nell's working prototype and full-time start, 4-year vesting with a 1-year cliff, and both founders' IP promised to the company.
They incorporate in March with 20,000 ordinary shares — 13,000 to Nell, 7,000 to Dominik — and adopt a shareholders' agreement restating the vesting, adding leaver provisions, transfer controls and reserved matters. The vesting clock runs from January, as the founders' agreement recorded.
At their £250,000 pre-seed the following year, the investor's refreshed shareholders' agreement supersedes everything earlier through its entire-agreement clause. One document now governs — and nothing agreed in January was lost on the way.
Where founders go wrong
Treating the two documents as interchangeable.
The founders' agreement records intent; the SHA and articles carry the machinery. Most teams need both, in sequence.Running both in parallel.
An SHA without an entire-agreement clause leaves two overlapping contracts alive — and a contradiction for a dispute to exploit.Losing the vesting start date in the handover.
If the SHA restarts the clock at signing, founders quietly lose months of vested equity. Carry the original date across.Never upgrading.
A two-page founders' agreement still governing at a priced round is a gap investors will make you fix — on their terms, mid-negotiation.
Related questions
What does a founders' agreement cover?
The founder-to-founder deal: who does what, the equity split and its logic, intended vesting, full-time commitment, and a promise that IP lands in the company. It is deliberately light — a record of the agreement while goodwill is high, not the machinery that enforces it. [More: What is a founders' agreement and do we need one?]
What should a shareholders' agreement include?
For a UK startup: the cap table position, founder vesting with good and bad leaver provisions, transfer controls and pre-emption, drag-along and tag-along, reserved matters, board arrangements, information rights and deadlock resolution — plus deeds of adherence binding every future shareholder to the same rules. [More: What should a shareholders' agreement include for a UK startup?]
Is a founders' agreement legally binding?
Yes, if signed as a proper contract — but it binds the founders personally and cannot compel a company that did not exist when it was signed. That is why its key terms are restated in the shareholders' agreement and articles once the company is incorporated.
Where should vesting live — founders' agreement or shareholders' agreement?
Agree the schedule in the founders' agreement so the intent is on paper, then implement it in the shareholders' agreement or articles, where buyback-at-nominal-value mechanics actually work. In the UK that means reverse vesting: founders own their shares from day one, subject to clawback. [More: What is founder vesting and how does it work in the UK?]
How do new shareholders join the shareholders' agreement?
By signing a deed of adherence — a short deed under which the incoming shareholder agrees to be bound by the existing agreement as if an original party. It should be a condition of every allotment or transfer, keeping one set of rules across the whole cap table. [More: What is a deed of adherence?]
The gap between these two documents is where founder disputes breed: intent recorded in one place, machinery missing from the other. A SuLe solicitor can check that your split, vesting and leaver terms actually survive the journey from founders' agreement to shareholders' agreement. Get your founder documents reviewed — book a free consultation and close the gap before an investor or a dispute finds it.
Keep reading: How should co-founders split equity in a UK startup? · What are good leaver and bad leaver provisions? · What happens to a co-founder's shares if they leave? · What is reverse vesting? · Should I use model articles or bespoke articles of association? · What legal documents does a UK startup actually need?
Primary sources: Companies Act 2006 · GOV.UK — Running a limited company
