What is a deed of adherence?
By SuLe · Updated 24 June 2026
A deed of adherence is a short legal document by which a new shareholder agrees to be bound by the company's existing shareholders' agreement, as if they had been an original party to it. It is standard practice whenever shares are issued or transferred to someone new, so the whole cap table stays governed by the same rules.
Key facts
- A deed of adherence binds a new shareholder to the existing shareholders' agreement as if they had signed it from the start.
- It is used whenever shares are issued or transferred to someone new — an investor, a late co-founder, or a hire.
- It is a deed rather than a contract because a deed does not require consideration to be binding.
- Without it, a new shareholder may not be bound by terms like drag-along, tag-along and leaver provisions.
- A good shareholders' agreement includes the form of deed as a schedule and requires new holders to sign one.
What is a deed of adherence, exactly?
It is the mechanism that keeps a growing shareholder base under one rulebook. Rather than reopening and re-signing the whole shareholders' agreement every time someone new comes on, the newcomer signs a one- or two-page deed that plugs them into the existing agreement.
The effect is that the new shareholder takes on the same obligations and enjoys the same benefits as the founders who signed originally. Transfer restrictions, drag-along and tag-along rights, reserved matters and confidentiality all apply to them from the moment they sign.
It is short by design. The heavy lifting lives in the shareholders' agreement; the deed simply says "I agree to be bound by all of that."
When do you need a deed of adherence?
Whenever someone becomes a shareholder who was not already a party to the agreement. That covers a new investor coming in at a round, a co-founder added after incorporation, and an employee or adviser who receives or exercises into shares.
Most shareholders' agreements make it a condition: no one is registered as a member until they have signed a deed of adherence. That is deliberate, because it stops unbound shareholders quietly accumulating on the register.
It applies to transfers as well as new issues. If a founder sells or gifts shares to someone outside the agreement, that buyer should sign a deed before the transfer is registered.
What does a deed of adherence contain?
Very little, because it borrows everything from the main agreement. Typically it identifies the new shareholder, the shares they are acquiring, and confirms they agree to be bound by the shareholders' agreement as if named in it from the outset.
It usually also confirms the new shareholder gets the benefit of the agreement's protections, not just its burdens — the arrangement runs both ways.
| Element | What it does |
|---|---|
| The new shareholder's details | Identifies who is joining and the shares acquired |
| Agreement to be bound | Ties them to the existing shareholders' agreement as an original party |
| Benefit of the agreement | Confirms they also receive its protections |
| Execution as a deed | Signed, witnessed and delivered — no consideration needed |
| Reference to the main agreement | Points to the agreement being adhered to, by date and parties |
Why a deed rather than an ordinary contract?
Because of a technicality that matters. An ordinary contract needs consideration — something of value passing between the parties — to be binding, and a new shareholder often gives nothing directly to the existing shareholders.
Using a deed removes that problem. A deed is binding without consideration, provided it is executed with the right formalities: in writing, signed, witnessed and delivered.
That is why the document is drafted as a deed of adherence and not a letter or side agreement. The form is chosen precisely to close off any argument that the newcomer's promises are unenforceable.
Worked example
Gemma runs a marketing-SaaS company with two co-founders under a shareholders' agreement containing drag-along rights — a term letting a majority force a minority to sell in an exit. An angel, Callum, invests and receives new shares.
At the point of issue, Callum signs a deed of adherence, becoming bound by the shareholders' agreement as if he had signed it originally. Under the Companies Act 2006 the company updates its register of members and cap table to record him.
Two years later a buyer wants 100% of the company. Because Callum signed the deed, the drag-along applies to him and he must sell alongside the founders. Had he never signed, he could have refused — holding up the whole sale from a minority position.
Where founders go wrong
Issuing shares without a deed.
A new shareholder who never signs may not be bound by drag-along, tag-along or leaver terms — a gap that can block a later sale.Forgetting transfers.
It is not only new investors. Anyone receiving transferred shares from outside the agreement should sign a deed too.Using a plain letter instead of a deed.
Without deed formalities and consideration, the newcomer's promise may be unenforceable. Execute it properly as a deed.No form of deed in the agreement.
If the shareholders' agreement does not include the deed as a schedule and require it, adherence gets skipped in the rush of a round.
Related questions
When do I need a deed of adherence?
Whenever someone new becomes a shareholder — a new investor, a co-founder joining after incorporation, or a hire receiving shares. It binds them to the existing shareholders' agreement so everyone is playing by the same rules. Without it, the newcomer is not bound by terms like drag-along or leaver provisions. [More: How do I add a new co-founder after incorporation?]
What does a deed of adherence do?
It makes a new shareholder a party to the existing shareholders' agreement as if they had signed it originally. They take on the same obligations and benefits — transfer restrictions, drag-along and tag-along, reserved matters, confidentiality — without the parties having to renegotiate or re-sign the whole agreement. [More: What should a shareholders' agreement include for a UK startup?]
Why is it a deed and not just an agreement?
A deed is used because it does not require consideration — something of value passing between the parties — to be binding. A new shareholder often gives nothing to the existing parties directly, so a deed avoids any argument that the promise is unenforceable for lack of consideration.
What happens if a new shareholder doesn't sign one?
They may not be bound by the shareholders' agreement at all. That can leave them free to ignore drag-along, tag-along, transfer restrictions and leaver terms — which can block a sale or fundraise later, exactly when you need everyone aligned. The gap is easy to create and painful to fix. [More: What are drag-along and tag-along rights?]
Who prepares the deed of adherence?
Usually the company or its solicitor, because the shareholders' agreement typically requires any new shareholder to sign one before they are registered. A well-drafted agreement includes the form of deed as a schedule, so it is simply completed and signed each time shares change hands. [More: What is a cap table and how do I keep it clean?]
A deed of adherence is two pages that can decide whether a minority shareholder can hold your exit hostage — skip it and an unbound holder sits outside your drag-along at the worst moment. A SuLe solicitor can build the deed into your shareholders' agreement and make sure every new holder signs before they hit the register. Get your founder documents reviewed — book a free consultation and keep your whole cap table under one rulebook.
Keep reading: What should a shareholders' agreement include for a UK startup? · How do I add a new co-founder after incorporation? · What is a cap table and how do I keep it clean? · Founders' agreement vs shareholders' agreement — what's the difference? · What are drag-along and tag-along rights? · How do I issue new shares in a UK company?
Primary sources: Companies Act 2006 · GOV.UK — Running a limited company
