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Share Investment Agreement UK: Key Terms Explained

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Written by Brad Askew Solicitor (non-practising)
Brad is on the roll of solicitors of England & Wales but does not hold a practising certificate and does not provide legal advice.
Updated June 2026 · England & Wales
When someone puts money, or their time and skills, into a company in return for shares, both sides need to know exactly what they are agreeing to. That is the job of a Share Investment Agreement. It sets out the size of the investment, the shares being issued, and the rights and obligations that come with them. For founders raising early capital, and for investors backing a growing business, this document is often the backbone of the whole deal. In this guide I walk through what these agreements typically cover, the two main flavours you will come across in the UK (cash and sweat equity), and the supporting paperwork that usually sits alongside them. It is written for company directors, founders, and individual investors who want to understand the shape of a deal before they sign.

What this document is

A Share Investment Agreement is the contract that records the terms on which a company issues new shares to an investor. In practical terms, it links three things together: the money or value the investor is putting in, the number and class of shares they receive in return, and the promises each side makes about the company and the deal.

You will often see these agreements used by startups and growing private companies in England and Wales when they take on angel investors, friends-and-family money, or an early institutional round. The agreement itself does a lot of work. It will usually record warranties given by the company and founders, any conditions that need to be satisfied before completion, restrictions on what the company can do after the money lands, and details about how the shares are allotted and registered.

For smaller deals it might sit alongside, or be combined with, a shareholders' agreement. For larger rounds you are more likely to see a standalone subscription agreement, a shareholders' agreement, and updated articles of association all working together. Whichever form it takes, the aim is the same: give both sides a clear written record of what has been agreed.

How to use this document

  1. Agree the commercial terms first. Before anyone drafts a document, the investor and company should align on the basics: how much is going in, what percentage of equity the investor gets, the valuation behind that split, and whether the investment is cash, services, or a mix. Writing these points down in a short term sheet saves significant time and legal cost later.
  2. Check the company's existing constitution. Look at the articles of association and any current shareholders' agreement. These may contain pre-emption rights, consent requirements, or restrictions on issuing new shares. If existing provisions get in the way, you may need shareholder consent or a formal waiver before the new shares can be allotted.
  3. Draft the agreement and supporting documents. The Share Investment Agreement itself needs to reflect the commercial deal, but it rarely sits alone. Expect to prepare board minutes approving the allotment, a written shareholders' resolution where needed, updated articles if share rights are changing, and a stock transfer or allotment record for the company's statutory books.
  4. Complete the deal and issue the shares. On completion the investor pays the agreed amount (or begins providing the agreed services), the board formally allots the shares, and the company updates its register of members. The investor should receive a share certificate, and the directors should keep copies of every signed document with the company records.
  5. File the changes with Companies House. After an allotment of shares, the company must file a return of allotments using form SH01 within one month. If the articles have been amended, the updated version must also be filed. Keeping Companies House up to date is a statutory duty and protects the validity of the investment on the public record.

Common questions

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Common questions

Q What is the difference between a Share Investment Agreement and a Shareholders' Agreement?
A Share Investment Agreement focuses on the moment of investment: the money coming in, the shares going out, and the promises made around that specific transaction. A Shareholders' Agreement is a longer-term document that governs how shareholders relate to each other and the company over time, covering things like decision making, transfers of shares, and exit. Many deals use both, and they are often signed together.
Q Can someone invest by providing services instead of cash?
Yes. Arrangements where shares are issued in return for services are often called sweat equity. They are useful when a company needs skills or work it cannot pay for in cash, for example marketing, development, or mentoring from an experienced founder. The agreement needs to describe the services clearly, set expectations about delivery, and deal with tax implications, which can be more complex than a straightforward cash subscription.
Q Do I need shareholder approval to issue new shares?
It depends on the company's articles and the Companies Act 2006. Directors often need specific authority to allot shares, and existing shareholders may have pre-emption rights giving them first refusal on new shares. These rights can sometimes be disapplied by a written resolution. Check the articles and any shareholders' agreement carefully before agreeing new share issues, as getting the authorisations wrong can cause real problems later.
Q What are warranties and why do they matter?
Warranties are statements of fact that the company and often the founders give about the business, for example that the accounts are accurate, that the company owns its intellectual property, and that there is no undisclosed litigation. If a warranty turns out to be untrue, the investor may have a claim for breach of contract. From an investor's perspective they reduce risk; from a founder's perspective they need to be given carefully and with appropriate limits.
Q Does a Share Investment Agreement need to be filed publicly?
The agreement itself is a private contract and is not filed at Companies House. However, the consequences of the deal often are. A return of allotments on form SH01 must be filed after shares are issued, updated articles must be filed if they change, and changes to people with significant control must be reported. So while the deal terms stay private, the resulting share structure becomes part of the public record.
Q Are there tax reliefs available for investors?
In some cases yes. Schemes such as SEIS and EIS can offer significant tax reliefs to qualifying investors in qualifying companies, and there are strict rules about the kind of shares issued, the use of the funds, and the company's size and trade. These rules change from time to time and the detail matters. Anyone planning to rely on a tax relief should check the current HMRC guidance and consider taking professional tax advice.
Q What happens if the investor and founders fall out later?
This is exactly why a well-drafted agreement matters. A good Share Investment Agreement, usually paired with a shareholders' agreement, will anticipate common friction points: decisions that need investor consent, what happens if a founder leaves, transfer restrictions, and how disputes are resolved. The time to negotiate these points is before the money changes hands, when goodwill is at its highest.
If you're dealing with this kind of situation, speak to an experienced legal adviser who can walk you through it — from £89.

Sources

This guide is based on primary UK law and official guidance.

Brad Askew, Solicitor (non-practising)

Written & reviewed by

Brad Askew Solicitor (non-practising)

Brad is on the roll of solicitors of England & Wales but does not hold a practising certificate and does not provide legal advice. LegalDocuments.co.uk is not a law firm and does not provide regulated legal advice.

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Legal disclaimer
This article is for general information only. It is a tool to help you find your way — not legal advice, and not a substitute for speaking to a qualified adviser about your situation.