Share Purchase Agreement (SPA): Key Clauses And When You Need One In The UK

If you’re buying or selling shares in a UK company, it can feel like you’re “just transferring ownership” and the rest will sort itself out later.

In practice, that’s where disputes (and expensive surprises) tend to start.

A Share Purchase Agreement (often shortened to “SPA”) is the main legal contract used to document a share sale and protect both sides. If you’ve been searching for a Share Purchase Agreement (SPA), you’re probably trying to work out what this document actually does, what needs to go into it, and when it’s worth getting one drafted properly.

Below, we break down what a Share Purchase Agreement is, when your business needs one, and the key clauses that matter most for small businesses and startups in the UK.

What Is A Share Purchase Agreement (SPA) In The UK?

A Share Purchase Agreement (SPA) is a legally binding contract where a seller agrees to sell and a buyer agrees to buy a specified number of shares in a company, on agreed terms.

Those shares might be:

• All shares (a full company sale), or
• Some shares (a partial sale, investment, or internal restructure).

In simple terms, a share purchase agreement sets out the “deal” and the rules for:

• what’s being sold (which shares and what rights attach to them)
• how much is being paid (and when)
• what the seller is promising about the business (warranties and disclosures)
• what happens if something is untrue or goes wrong later
• what has to happen at completion (so the buyer actually becomes the legal owner)

While some share sales are straightforward (for example, one shareholder selling to another shareholder), even “simple” deals can get messy without clear terms. The SPA is the document that keeps everyone on the same page.

It’s also worth noting: an SPA is usually only one part of the bigger picture. Depending on your deal, you may also need:

• updated company constitutional documents like the articles of association
• a Shareholders Agreement to govern the relationship after the sale
• board and shareholder approvals (often recorded via resolutions)
• the practical mechanics of the Share Transfer

When Does Your Business Need A Share Purchase Agreement?

Not every share transfer needs a long, complex SPA. But if money is changing hands and the business has any real operating risk, a properly drafted Share Purchase Agreement is usually a smart move.

Common scenarios where a share purchase agreement is especially important include:

1) You’re Buying Or Selling A Company (Full Acquisition)

If the buyer is buying 100% of the shares (or a controlling stake), they’re effectively taking over the whole company: assets, contracts, liabilities, employees, tax history, and all.

The SPA is where the buyer will want strong warranties, disclosure protection, and clear completion mechanics.

2) A Co-Founder Or Shareholder Is Exiting

It’s common for startups and small companies to have an early shareholder leave. Maybe they’re moving on, retiring, or there’s a dispute.

An SPA can document the price, timing, handover obligations, and protections for both sides. In some exits, a Deed of Settlement may also be relevant if the exit is part of resolving wider issues.

3) You’re Bringing In An Investor By Selling Existing Shares

Sometimes investment happens via issuing new shares (a subscription). Other times, an investor buys existing shares from founders or early shareholders.

If the investor is buying existing shares, you’ll typically use an SPA (and often also update or enter into a Shareholders Agreement to reflect new rights and decision-making rules).

4) You’re Doing An Internal Restructure

Group restructures, moving ownership between family members, or reorganising holdings across entities can still require a share sale document (even if the price is nominal) to record the transfer clearly and manage tax and risk issues.

5) The Deal Has Deferred Consideration Or Earn-Out

If the buyer is paying in instalments, holding back part of the price, or paying an earn-out based on future performance, you need a contract that is crystal clear about how that will work.

This is one of the easiest areas for disputes to arise if the wording is vague.

As a general rule, if you’re relying on “we trust each other”, that’s usually a sign you should still get the legal foundations right. Trust is great - but a clear SPA protects relationships as much as it protects money.

Key Clauses In A Share Purchase Agreement (SPA) (And Why They Matter)

There’s no single “standard” SPA that fits every deal. But most UK SPAs include a set of core clauses, plus extras depending on what’s being sold and the risks involved.

Below are the clauses that most often matter for small businesses.

Parties, Shares And Sale Mechanics

This section identifies:

• who the seller(s) are
• who the buyer(s) are
• exactly which shares are being sold (including share class)
• whether any shares are subject to restrictions, pre-emption rights, or consents

This might sound basic, but “which shares” can get complicated if your company has different classes (A/B shares), different voting rights, or past informal transfers.

Price, Consideration And Payment Terms

The SPA should be clear on the purchase price and how it’s paid, for example:

• a lump sum on completion
• deferred payments over time
• earn-out payments linked to revenue, profit, or milestones
• retention amounts withheld to cover warranty claims

If there’s an earn-out, you’ll want to define:

• the calculation method (and accounting principles)
• access to management accounts
• who controls the business during the earn-out period
• what happens if the buyer changes the business model (which can affect earn-out performance)

Completion, Deliverables And Company Approvals

Completion is the moment the share sale actually happens.

The SPA usually sets out a “completion checklist” style schedule: what documents must be signed and exchanged, what approvals are needed, and what the company’s records must show afterwards.

This often includes items like:

• signed stock transfer forms
• board minutes and resolutions
• updating the register of members
• issuing new share certificates (if relevant)

For many deals, it’s also sensible to prepare clear board approvals using a Directors Resolution approach (tailored to your transaction), so it’s properly recorded that the company and directors have authorised what needs to happen.

Warranties (Seller Promises About The Business)

Warranties are statements the seller makes about the company - for example that:

• the company owns the assets it says it owns
• accounts are accurate (or at least not misleading)
• there are no undisclosed legal disputes
• tax has been handled properly
• contracts with customers and suppliers are valid and not in default
• there are no hidden liabilities

From a buyer’s perspective, warranties are a key protection: if a warranty turns out to be untrue, the buyer may be able to claim compensation (depending on how the SPA is drafted).

From a seller’s perspective, warranties need to be carefully limited so you’re not accidentally promising more than you can safely stand behind.

Disclosure Letter (What The Seller Tells The Buyer Upfront)

In many deals, the seller provides a disclosure letter (or disclosures) that qualify the warranties.

For example, the SPA might say “there is no litigation”, but the disclosure letter might disclose that a particular dispute exists. If an issue is properly and fairly disclosed in line with the SPA, it will often limit (or prevent) a buyer from bringing certain warranty-based claims about that specific disclosed matter.

This is one of the main reasons you should avoid DIY templates for a Share Purchase Agreement. The protections often come down to how warranties and disclosures “talk to each other”.

Indemnities (Specific Risk Allocation)

Indemnities are often used where there is a known, specific risk - and the buyer wants the seller to cover that risk if it crystallises.

For example, if there’s a known tax issue under review, the buyer may ask for a tax indemnity.

Indemnities are usually more “buyer-friendly” than warranties, so they should be negotiated carefully and drafted precisely.

Restrictive Covenants (Non-Compete, Non-Solicit)

If you’re selling your business, the buyer may want to make sure you don’t sell the goodwill and then immediately set up a competing business across the road.

Restrictive covenants in an SPA often cover:

• non-compete obligations
• non-solicitation of customers/suppliers
• non-poaching of staff
• confidentiality

These clauses must be reasonable and tailored to be enforceable (for example, in scope, duration, and geography). Overreaching restrictions can be difficult to enforce.

Limitation Of Liability (Caps, Time Limits, Knowledge)

Limitation clauses usually set the boundaries for claims, such as:

• a maximum cap on liability (often linked to the purchase price)
• time limits for bringing claims (for example, 12–24 months for general warranties, longer for tax)
• minimum claim thresholds (so small claims don’t trigger disputes)
• rules about what the buyer must do to mitigate loss

This section is often one of the most negotiated parts of an SPA because it directly affects your risk after completion.

Conditions Precedent (If The Deal Needs Things To Happen First)

Sometimes an SPA is signed now, but completion happens later, once certain conditions are met. For example:

• third-party consents are obtained (landlord, bank, key customer)
• regulatory approvals are received (industry dependent)
• internal consents are completed
• pre-completion restructure steps occur

If you need a gap between signing and completion, the agreement should also deal with what happens in that “in-between” period, including how the company is run and what approvals are needed for major decisions.

How Does A Typical Share Purchase Agreement Process Work?

Every deal is different, but most UK share sales follow a similar flow. If you’re time-poor (and most business owners are), this can help you see the transaction as a series of manageable steps.

Step 1: Agree Heads Of Terms (Commercial Deal First)

Before drafting the SPA, the parties often agree key commercial terms such as price, timing, and major conditions. This helps reduce the risk of legal drafting going around in circles.

Step 2: Due Diligence (Checking What’s Really Being Bought)

Buyers usually want to review key areas of the business: company records, contracts, finance, tax, employment, disputes, and IP ownership.

This is where a structured Legal Due Diligence process can be a big help, because it’s far easier (and cheaper) to address issues before signing than to argue about them afterwards.

Step 3: Draft And Negotiate The SPA (And Supporting Documents)

The SPA is drafted to reflect the deal and the risk allocation the parties agree on. Supporting documents might include:

• disclosure letter
• board minutes/resolutions
• updated articles of association
• new or updated shareholders agreement

Depending on the structure, you might also need other transaction documents (for example, a consultancy agreement for handover support, or updates to constitutional documents) so everything works together cleanly.

Step 4: Signing

Once the SPA is agreed, the parties sign. If completion is simultaneous, signing and completion happen at the same time. If there are conditions precedent, signing may happen first and completion later.

If you’re unsure about formalities (including whether any document needs to be executed as a deed), it’s worth making sure execution is handled correctly under English law - because mistakes can cause real enforceability issues later.

Step 5: Completion (Ownership Changes Hands)

Completion is when the buyer becomes the owner of the shares. The company’s statutory books and registers are updated, and the purchase price is paid as agreed.

Step 6: Post-Completion (Earn-Outs, Transitional Support, Ongoing Obligations)

If there are deferred payments, warranties that survive, or transitional obligations (like the seller helping hand over relationships), the SPA will continue to govern the relationship after completion.

Common Mistakes In Share Purchase Agreements (And How To Avoid Them)

Most SPA disputes aren’t caused by bad intentions. They’re caused by assumptions.

Here are a few common traps we see, especially in small business share sales.

Relying On Generic Templates

A template might look “legal enough”, but it won’t reflect your deal-specific risk profile (especially on warranties, disclosures and limitation of liability).

In a share sale, small drafting differences can materially change who wears the risk.

Not Checking The Company’s Existing Restrictions

Many companies have restrictions on share transfers in their articles or shareholders agreement (like pre-emption rights or director consent requirements).

If you don’t follow those rules, the transfer can be challenged or delayed.

Vague Earn-Out Or Deferred Payment Clauses

If the SPA says “earn-out based on profit” but doesn’t define profit (and doesn’t set out the accounting treatment), you’re leaving the door wide open to disagreement later.

Ignoring Tax And HMRC Risks

Share sales can have significant tax implications (for both buyer and seller). SPAs often include tax warranties and sometimes tax indemnities, but those clauses don’t replace tax advice.

In practice, you want your legal documents and tax advice working together. (This article is general information only and isn’t tax advice.)

Forgetting What Happens After Completion

If the seller is staying on as a director, consultant, or employee, you may also need separate agreements to document the ongoing relationship (role, pay, confidentiality, termination rights). If you don’t, you risk confusion about authority and expectations from day one.

Key Takeaways

• A Share Purchase Agreement (SPA) is the core contract used to document a share sale in a UK company and protect both buyer and seller.
• You’ll usually want an SPA when the deal involves meaningful money, risk, deferred consideration, a full company sale, or a shareholder exit.
• Key SPA clauses typically cover price and payment mechanics, completion steps, warranties and disclosures, indemnities, restrictive covenants, and limits on liability.
• Due diligence and a proper disclosure process are often what prevent disputes later - they help align expectations before signing.
• Share transfers can be restricted by existing articles or shareholder arrangements, so it’s important to check the company’s documents before agreeing a deal.
• DIY templates often miss the details that matter most in a share sale, so it’s worth getting the SPA drafted or reviewed to fit your transaction.

If you’d like help drafting or reviewing a Share Purchase Agreement, or you’re not sure what documents your deal needs, you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.