How to Build a Founder Agreement Between Co-Founders: The Complete Guide

A founder agreement (also called a co-founder agreement or founders' shareholders agreement) is a private, legally binding contract between the founding members of a startup. It establishes the terms of the business relationship, clarifies expectations, and provides mechanisms for resolving disputes or managing departures.

Unlike your company's articles of association, which are public documents filed with Companies House, a founder agreement is typically confidential and more detailed. It addresses the practical, day-to-day realities of running a business together—from how decisions get made to what happens if a founder leaves.

The statistics are stark: 65% of high-potential startups fail due to conflicts between co-founders. Common triggers include:

• Disagreements over equity distribution
• Misaligned expectations about roles and time commitment
• Disputes over strategic direction
• One founder leaving early but retaining significant equity
• Intellectual property ownership disputes

A founder agreement addresses all of these scenarios proactively, establishing clear protocols before emotions run high or financial stakes increase.

The ideal time to create your founders agreement is before you formally incorporate your business. At this stage, discussions are typically more amicable, valuations are low, and everyone is motivated to reach fair terms.

However, if you've already incorporated, don't panic—it's never too late to create a founder agreement. Many startups formalise their agreements shortly after incorporation or even before their first funding round. The key is to act before any conflict arises.

A comprehensive founder agreement should cover multiple key areas. Here's what to include:

How you divide equity is often the most sensitive—and most important—part of your founders agreement.

Common approaches:

• Equal split: Simple but potentially problematic if contributions are unequal (50/50, 33/33/33)
• Weighted split: Based on factors like initial capital, domain expertise, time commitment, or idea origination
• Dynamic equity: Equity allocation adjusts over time based on ongoing contributions (complex to administer)

Best practices:

• Document the rationale behind your equity split—investors will scrutinise it
• Ensure everyone retains meaningful equity (typically at least 10-15% each) to maintain motivation through dilution
• Consider leaving 10-15% unallocated for an employee share option scheme (ESOP) before outside investment

A vesting schedule determines how founders earn their equity over time, rather than receiving it all immediately. This is arguably the most critical protection mechanism in any founder agreement.

Standard vesting terms:

• Duration: 4 years total vesting period
• Cliff: 1-year cliff (no equity vests before 12 months)
• Schedule: Monthly or quarterly vesting after the cliff
• Example: With a 4-year vesting schedule and 1-year cliff, if a founder leaves after 8 months, they receive 0% of their allocated shares. If they leave after 18 months, they keep 37.5% (the 25% that vested at month 12, plus half of year 2's 25%).

Why vesting matters:

Imagine two co-founders each own 50% equity. One founder quits after six months without a vesting schedule—they walk away with half the company despite minimal contribution. With vesting, they'd receive nothing (if within the cliff period) or only a proportional amount.

Acceleration means vesting speeds up under certain circumstances. The two main types are:

• Single-trigger acceleration: Vesting accelerates upon a specific event (e.g., acquisition), regardless of whether the founder stays
• Double-trigger acceleration: Requires two events (e.g., acquisition AND termination without cause within 12 months)

Recommendation: Double-trigger acceleration is more investor-friendly and more common. It protects founders from being forced out post-acquisition whilst ensuring they remain incentivised to help with the transition.

Clearly define each founder's role, title, responsibilities, and time commitment.

Include:

• Official titles (CEO, CTO, COO, etc.)
• Key responsibilities and decision-making authority
• Time commitment expectations (full-time vs. part-time; percentage of time)
• Reporting relationships if applicable
• Performance expectations

Why this matters:

Vague role definitions lead to duplicated effort, accountability gaps, and resentment. If one founder expects everyone to work full-time whilst another plans to keep their day job, that's a recipe for conflict.

This clause is often overlooked—but it's critical. Under UK law, intellectual property (IP) created by an individual belongs to that individual unless explicitly assigned to the company.

Your founder agreement should:

• Require all founders to assign any pre-existing IP relevant to the business to the company
• Commit founders to assign all future IP created during their involvement to the company
• Confirm this applies to code, designs, trademarks, patents, content, and any other proprietary materials
• Specify that moral rights (where applicable) are asserted but waived for commercial use

Define how decisions get made, especially in deadlock situations.

Common structures:

• Unanimous consent: Required for major decisions (fundraising, selling the company, taking on debt, hiring senior leadership)
• Simple majority: For operational decisions (budgets, hiring, vendor contracts)
• Casting vote: Give one founder (usually the CEO) a tie-breaking vote for specific categories
• Deadlock mechanisms: If unanimous consent is needed but not reached, specify mediation, arbitration, or buy-sell provisions

These provisions determine what happens to a departing founder's shares—and at what price.

Good leaver scenarios:

• Death or permanent disability
• Retirement (after a minimum period)
• Mutual agreement
• Termination without cause

Treatment: The company or remaining founders purchase vested shares at fair market value. Unvested shares are forfeited.

Bad leaver scenarios:

• Gross misconduct or breach of duties
• Resignation without good reason
• Termination for cause
• Competing with the business

Treatment: The company or remaining founders can purchase all shares (vested and unvested) at a discount—often nominal value (e.g., £0.01 per share).

Medium leaver scenarios:

• Some agreements add a middle category for resignations or performance-related terminations
• Treatment: Vested shares purchased at fair value with a modest discount (e.g., 20-30%); unvested shares forfeited

These clauses prevent departing founders from immediately competing against the company or poaching employees/customers.

Key considerations:

• Duration: Typically 6-12 months (longer periods may be unenforceable)
• Geographic scope: Must be reasonable—UK-only or specific territories
• Activity scope: Define what constitutes "competing" precisely
• Financial compensation: For enforceability, especially if the founder is also an employee, compensation may be required

Require founders to:

• Keep all business information confidential during and after their involvement
• Comply with data protection laws (GDPR)
• Return all company property and data upon departure

Specify how disputes will be resolved:

1. Negotiation: Direct discussion between founders (30-60 day period)
2. Mediation: Independent mediator facilitates resolution
3. Arbitration or litigation: Final binding resolution

Arbitration is often preferred because it's faster, private, and less expensive than court litigation.

Drag-along rights: Allow majority shareholders to force minority shareholders to sell their shares in an acquisition, preventing one founder from blocking a valuable exit.

Tag-along rights: Protect minority shareholders by allowing them to join a sale on the same terms if majority shareholders are selling.

Both provisions ensure fair treatment during exit scenarios.

Before drafting anything, sit down with your co-founders and discuss:

• Your vision and values for the business
• Individual goals, expectations, and commitment levels
• How you'll handle disagreements
• What success looks like for each person
• Financial expectations and timelines

These conversations build trust and surface potential misalignments before they become entrenched.

Whilst you should never rely solely on templates, they provide a useful starting point. Resources include:

• UK-specific founder agreement templates from reputable legal publishers
• SeedLegals and other startup legal platforms
• Templates from law firms (often available on their websites)

Based on your discussions and research, create a first draft covering all essential clauses outlined above. Be specific—vague language leads to disputes.

This step is non-negotiable. Have a solicitor specialising in corporate or startup law review your agreement. They'll ensure:

• Compliance with UK company law and employment law
• Enforceability of all clauses
• Protection against common pitfalls
• Appropriate tax treatment

Professional legal review typically costs £1,000-£3,000 depending on complexity, your solicitor's seniority, and location—a worthwhile investment compared to the significant costs and business disruption of founder disputes and litigation.

Your solicitor may recommend changes. Discuss these with your co-founders, negotiate any sticking points, and finalise the document.

All founders must sign the agreement. Execute it using a reliable method—electronic signatures like Yousign's legally binding e-signature solution streamline this process whilst ensuring compliance and creating an audit trail.

Store signed copies securely—you'll need them for investor due diligence.

Whilst drafting your founder agreement requires careful thought and legal expertise, executing it shouldn't be complicated. Once you've finalised your document with your solicitor, the signing process should be seamless, professional, and investor-ready.

Creating a founder agreement is a complex legal task that protects your startup's future—but signing it doesn't have to be. Imagine you and your co-founder are in different cities—one in London, one in Edinburgh. With traditional paper-based signing, you'd need to print multiple copies, courier them back and forth, and wait days for wet signatures. That delay can stall incorporation, delay bank account opening, and create unnecessary friction at a critical moment.

Investors increasingly expect startups to have clean, digitally-signed documentation from day one. A paper-based founder agreement with scanned signatures raises red flags during due diligence. It suggests either outdated processes or, worse, documentation created retrospectively after problems emerged. Electronic signature demonstrates professionalism, forward-thinking operations, and proper governance—exactly what Series A investors look for.

Yousign's electronic signature solution enables you to:

• Execute agreements instantly: Send your founder agreement for signature and receive signed copies within minutes, not days. Both founders can sign from anywhere, on any device, removing geographic and logistical barriers.
• Maintain a complete audit trail: Every signature is timestamped and securely logged with IP addresses, device information, and authentication details—providing irrefutable evidence of when and how the agreement was signed. This audit trail is critical during investor due diligence.
• Ensure legal compliance: Yousign's advanced electronic signatures comply with eIDAS regulation, making them legally binding and admissible in UK courts for business documents.
• Streamline investor due diligence: Store all signed agreements in one secure location, easily accessible when investors request documentation. No scrambling to find filed papers or reconstruct signature dates—everything is digital, organised, and investor-ready.

With Yousign, you can focus on building your business whilst ensuring all your founding documents are properly executed, legally compliant, and investor-ready from day one.

Many founders confuse these two documents. Here's how they differ:

You may start with a founder agreement and later replace or supplement it with a shareholders' agreement when outside investors join. However, founder-specific provisions (like vesting schedules and role definitions) often remain in a separate document or schedule.

Your founder agreement isn't a "set it and forget it" document. Review and update it when:

• A new co-founder joins
• A founder's role or responsibilities change significantly
• The business pivots or changes direction
• You raise external funding (investors may require amendments)
• Employment status changes (e.g., a founder becomes an employee)
• You're approaching key vesting cliff dates
• Legal or regulatory requirements change

Plan to review your agreement at least annually, and always before major business milestones like fundraising rounds.

Yes—when properly drafted and executed, founder agreements are legally binding contracts under UK law. Courts will enforce them provided they:

• Are in writing and signed by all parties
• Include valuable consideration (something of value exchanged—equity typically satisfies this)
• Contain legal and reasonable terms
• Were entered into voluntarily without duress or misrepresentation

Courts may refuse to enforce clauses that:

• Impose unreasonable restraints of trade (overly broad non-compete clauses)
• Are illegal or contrary to public policy
• Are unconscionable or grossly unfair
• Lack sufficient specificity to be enforceable
• Were signed under duress, undue influence, or misrepresentation

This is why professional legal review is essential.

Strictly speaking, no—UK law doesn't require solicitor involvement to create a binding contract. However, in practice, the answer is yes. Startup law is complex, and mistakes can be expensive. A solicitor ensures your agreement is comprehensive, enforceable, and tailored to your specific circumstances.

Budget £1,000-£3,000 for solicitor review and customisation—money well spent to avoid potentially catastrophic disputes that can derail your business.

Creating a founder agreement is one of the most important early decisions you'll make. Here's how to move forward:

1. Schedule a founders' discussion: Openly discuss expectations, equity, roles, and commitment
2. Research templates and frameworks: Familiarise yourself with standard terms and structures
3. Consult a startup solicitor: Brief them on your business and goals; review draft agreements together
4. Negotiate transparently: Address concerns early with open, honest communication
5. Execute and store securely: Sign using a legally compliant method and keep copies accessible

Useful resources:

• SeedLegals (seedlegals.com): UK-focused startup legal platform with templates and guidance
• British Business Bank (british-business-bank.co.uk): Resources for startups and early-stage businesses
• TechNation (technation.io): UK tech ecosystem support and resources
• Law firms specialising in startups: Osborne Clarke, Taylor Vinters, Gunderson Dettmer

A founder agreement is more than a legal formality—it's the foundation of trust, clarity, and fairness that enables co-founders to build something meaningful together. By defining equity, roles, decision-making processes, and exit scenarios upfront, you prevent conflicts before they arise and position your startup for long-term success.

Don't wait until problems emerge. Create your founder agreement now, involve legal experts, be transparent with your co-founders, and execute it properly. Your future self—and your business—will thank you.