A UK funding round often brings several investors together, so founders and angels regularly meet a co-investment agreement, whether or not the document carries that name.
We think it pays to understand how a round gets shared before the paperwork lands. This guide covers the lead investor vs co-investor split, what gets documented, and where SEIS and EIS change the picture.
What Is a Co-Investment Agreement?
A co-investment agreement is a contract under which two or more investors fund the same company or deal side by side, usually on terms a lead investor negotiates. The phrase carries two meanings.
In a startup round, it describes investors joining a lead’s deal. In private equity, Cambridge Associates defines co-investing as limited partners investing in a company alongside the fund manager, most often through a special purpose vehicle.
How Co-Investment Works in Venture Capital
Co-investment in venture capital means several investors fund one round, with a lead investor negotiating the terms and running most of the due diligence.
The other investors join on those terms and rely largely on the lead’s work. For UK Series A rounds, the model documents from UK Private Capital (formerly the BVCA) set the usual template: a subscription agreement, shareholders’ agreement and articles of association, plus a summary of terms added in the update of 26 February 2025.
Memery Crystal noted that the 2023 subscription agreement was structured for a lead investor, as is typical at Series A.
Lead Investor vs Co-Investor: Roles, Rights and Responsibilities
The lead investor sets the price and terms, runs the main due diligence and often takes a board or observer seat, while co-investors fund the round on those terms.
The lead investor vs co-investor split shapes governance too. Bird & Bird says an investor holding 5% to 10% or more might ask for board rights, as a rule of thumb. It adds that an observer seat gives access to board discussions and papers without a director’s statutory duties, and advises that unless you are the lead with a specific governance reason, observer rights are usually the sensible route.
Angel Investor Co-Investment in the UK
Angel investor co-investment in the UK often runs through syndicates, and the British Business Bank invests alongside them via its Regional Angels Programme (£285m total capital).
The programme typically commits £5m to £15m to partners, who invest the Bank’s money alongside their own and other investors’ (British Business Bank).
On 10 September 2026, the Bank said its Haatch-managed capital had reached £62m and that the Bank and Haatch had co-invested in 208 companies. The Bank’s matched capital lets Haatch’s funds add £85,000 to each £250,000 investment, which takes them past the typical SEIS cap.
In Scotland, external co-investors supplied 54% of the money raised in 2021 deals led by LINC Scotland member syndicates, while public investors, chiefly Scottish Enterprise, supplied about 20%.
What a Co-Investment Agreement Usually Covers
A co-investment agreement usually covers the share price and number, each investor’s board and information rights, consent matters, and protections such as pre-emption and anti-dilution.
UK rounds typically spread these terms across several documents:
- Board rights: the right to appoint a director or an observer.
- Information and consent: reporting rights and investor consent matters, which Bristows lists among the core shareholder terms.
- Protections: pre-emption and anti-dilution provisions, which Chambers describes as prevalent in UK venture deals (2025).
How Co-Investment Fits With the Term Sheet and Shareholders’ Agreement
The term sheet sets the headline terms, the subscription agreement completes the investment, and the shareholders’ agreement and articles govern the relationship afterwards.
Term sheets are usually non-binding, while the subscription and shareholders’ agreements bind the parties.
Memery Crystal described the 2023 BVCA subscription agreement as a one-off document and the shareholders’ agreement as the forward-looking one.
The 2023 model restricted pre-emption rights to Investors or Major Investors, and the February 2025 update added optional drafting on pre-emption waivers, so a smaller co-investor should check which category it falls into and whether the deal uses that option.
Review the term sheet, subscription agreement, shareholders' agreement and articles before completing an investment.
SEIS and EIS Considerations for Co-Investors
A co-investor can claim 50% income tax relief on up to £200,000 of SEIS shares a year, or 30% on up to £1 million of EIS shares. The EIS limit rises to £2 million if at least £1 million goes into knowledge-intensive companies.
Investors must hold newly issued, fully paid, full-risk ordinary shares for at least three years, and cannot be connected to the company: employees (with some director exceptions) and holders of more than 30% do not qualify.
GOV.UK also rules out arrangements to protect the investment, and relief depends on the company’s SEIS3 or EIS3 certificate.
In mixed rounds, check how a fund’s share rights sit alongside the full-risk ordinary shares that qualifying investors must hold.
Benefits and Risks for Founders and Investors
Co-investment lets founders raise larger rounds and lets investors share risk, but co-investors depend heavily on the lead investor’s diligence and judgement.
The British Business Bank says its matched capital lets Haatch write larger cheques at the earliest stages. Cambridge Associates, writing mainly about private equity, flags two points for co-investment in venture capital: co-investments there are more likely to carry fees, and alignment concerns can arise when a lead put most of its capital in at a lower valuation before bringing co-investors into a later round.
Common Mistakes to Avoid
The most common mistake is assuming every investor holds the same rights, when board seats and pre-emption can depend on shareholding or Major Investor status. The second is overlooking SEIS and EIS conditions: GOV.UK says investors lose relief if they sell shares within three years, develop a connection with the company or receive money or other assets from it, or if the company stops meeting the scheme conditions.
The third is miscounting company limits, because SEIS shares count as relevant investments towards the EIS limits (HMRC Venture Capital Schemes Manual). Check all three before completion.
Conclusion
We think a co-investment agreement matters most to investors who did not lead the round, because they inherit terms someone else negotiated.
The practical steps are straightforward: confirm who leads, check which rights each investor receives, and confirm that SEIS or EIS conditions survive the final share terms.
Co-investment in venture capital works best when everyone reads the shareholders’ agreement and articles, and angel investor co-investment in the UK is no different.
FAQs
1. What is a co-investment agreement?
A co-investment agreement is a contract under which two or more investors fund the same company or deal alongside each other, usually on terms a lead investor sets. In UK startup rounds, those terms usually sit in the subscription agreement, shareholders’ agreement and articles of association rather than one document.
2. What is the difference between a lead investor and a co-investor?
A lead investor sets the terms, runs the main due diligence and often takes a board or observer seat, while a co-investor funds the round on those terms. Bird & Bird notes that observer rights give board access without a director’s statutory duties.
3. Can angel investors co-invest in UK startups?
Yes, angel investors co-invest in UK startups, often through syndicates that the British Business Bank backs alongside its own capital. The Regional Angels Programme holds £285m of total capital, and by 10 September 2026 the Bank and Haatch had co-invested in 208 companies (British Business Bank).
Sources: GOV.UK and HMRC; British Business Bank (September 2026 release, Regional Angels Programme); Cambridge Associates (2023, updated March 2026); Bird & Bird (2025); Memery Crystal (2023); Burges Salmon and HSF Kramer (2025); Herbert Smith Freehills; Jonathan Lea Network; Bristows; Chambers (2025); Scottish Financial Review (2022). Figures reflect the latest available data at the time of writing, November 2026. General information only, not legal or tax advice.
The EP+ Editorial Desk covers UK startups, founder stories, and venture capital. All editorial content is independently produced and human-reviewed before publication.
