A shareholders agreement is a private contract between the shareholders of a company that governs how shares are owned, transferred, and exercised. It is separate from the articles of association (which are the public constitution filed at Companies House) and addresses the things that the articles do not, particularly the personal commitments between founders. For a UK tech startup, the absence of a proper shareholders agreement at formation is one of the highest-impact unforced errors a founder team can make.
Why the articles alone are not enough
The articles of association cover the formal mechanics of share rights, director appointments, and shareholder meetings. They are public, filed at Companies House, and visible to anyone. They are designed to govern the company as a legal entity.
The shareholders agreement covers what the articles deliberately do not:
- Vesting of founder shares over time.
- Good-leaver versus bad-leaver treatment when a founder departs.
- Founder commitments around full-time involvement and non-compete.
- Pre-emption rights on share transfers between shareholders.
- Drag-along and tag-along rights for exit transactions.
- Anti-dilution provisions for early investors.
- Information rights for non-employee shareholders.
- Specific decision-making rights that require unanimous or supermajority shareholder approval.
These are private commitments between the people who own the company. They do not need to be public. They do need to be in writing.
The single most important provision: vesting
Vesting means that founders' shares are not fully owned at incorporation. They become owned (vest) over time, conditional on the founder continuing to work for the company. The standard structure is four-year vesting with a one-year cliff: nothing vests in the first year, then 25% vests at the one-year anniversary, then the remaining 75% vests monthly over the following three years.
Vesting protects the company from the failure mode where one founder leaves early but retains a large slice of equity. Without vesting, a 50/50 split where one founder departs three months in leaves them with 50% of the company forever. With four-year vesting and a one-year cliff, that same departure leaves them with zero.
Investors require vesting
Standard angel and seed term sheets presume founder vesting is in place. If it is not, the term sheet will require it, and retrofitting vesting onto already-issued shares is messier than getting it right at formation. Investors who see un-vested founder cap tables either negotiate hard on the structure or walk away.
Good-leaver versus bad-leaver clauses
These define what happens to vested shares when a founder leaves. The standard distinction:
| Departure type | Vested shares treatment |
|---|---|
| Good leaver (death, disability, mutual termination, redundancy) | Founder keeps all vested shares |
| Bad leaver (resignation against contract, dismissal for cause, breach of agreement) | Company can buy back vested shares at lower of market value or par value |
The bad-leaver provision is what makes the difference between an amicable departure and a hostile one cost the company materially different things. Without it, even a founder fired for serious misconduct keeps their full vested equity at fair value.
Founder commitments and non-compete
A shareholders agreement typically requires each founder to:
- Devote substantially all their working time to the company.
- Assign all relevant intellectual property created in connection with the business.
- Not engage in competing activities during their tenure and for a defined period afterwards (typically 6 to 12 months).
- Not solicit employees, customers, or suppliers for a defined period afterwards.
The IP assignment is particularly critical. Without it, code or designs created by a founder before formal incorporation may technically belong to the founder personally rather than to the company. Investors require clean IP ownership in due diligence; founders without it discover during their first term sheet that they have a problem to fix.
Pre-emption, drag-along, and tag-along
Pre-emption rights
When the company issues new shares (in a funding round, for example), existing shareholders have the first right to buy them in proportion to their existing holdings. This prevents existing shareholders from being diluted involuntarily. It also creates a lever for negotiating round terms, since investors need to either negotiate around pre-emption or accept it.
Drag-along rights
When a majority of shareholders accept a sale of the company, they can "drag along" the minority into the same transaction. This prevents a small minority from blocking an exit. The threshold is usually 50% or 75% of shareholders, sometimes structured to require holders of preference shares to consent.
Tag-along rights
When a majority shareholder sells their stake, minority shareholders can "tag along" and sell at the same price. This protects minority shareholders from being left in the company after the controlling owner exits. The two work together: drag-along prevents minority obstruction, tag-along prevents majority abandonment.
When to put it in place
At incorporation, ideally. Definitely before the first co-founder is added. Definitely before any external money or share is exchanged for value. The cost of drafting a standard startup shareholders agreement is £500 to £1,500 from a startup-specialist solicitor, often less if your accountant has a templated approach.
The cost of negotiating one after a co-founder dispute, an early departure, or a first investor round is materially higher. The negotiation is harder because the parties' interests have already diverged.
A composite scenario
Two co-founders incorporate with 50/50 shares and no shareholders agreement. Three months in, one founder decides the project is not for them and leaves. They retain 50% of the equity. Two years later, the remaining founder has built the business to a £2m seed offer. The investor refuses to invest at that valuation until the cap table is restructured. The departed co-founder, knowing this, demands a substantial buyout. A standard four-year vesting with one-year cliff at incorporation would have left the leaver with zero shares automatically.
Common questions
Do solo founders need a shareholders agreement?
Not at incorporation. The shareholders agreement governs relationships between multiple shareholders. A solo founder with all shares does not need one until a second shareholder appears. Plan to have one drafted at the moment a co-founder, advisor, or investor joins.
Can I use a template?
Templates exist and are useful as starting points. Y Combinator publishes template founder agreements. Various UK-specific templates are available. They are usually 80% of the way to a usable agreement but the last 20% (specific share rights, director appointment rights, sector-specific provisions) needs adapting. Cheaper as a base for a solicitor than a blank sheet.
How does the shareholders agreement interact with the articles?
The articles control share rights at the corporate level. The shareholders agreement controls the personal commitments between owners. Where they overlap (for example, on share transfer restrictions), the articles typically prevail because they are the formal company constitution. Drafted properly, they complement each other.
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The Founder's Guide to UK Company Formation and StructureRead the complete guide and the rest of the series.