Unenforceable Contracts: What Makes a Contract Unenforceable and How to Avoid It

If you run a small business, contracts are part of everyday life. You might be signing up new customers, onboarding suppliers, collaborating with partners, or hiring your first team members.

Most of the time, you’re doing this to create certainty: who’s doing what, when they’ll do it, how much it costs, and what happens if something goes wrong.

But here’s the catch: not every agreement that looks like a contract will actually hold up if you need to enforce it. A poorly drafted or legally flawed agreement can end up being unenforceable - meaning you may struggle (or fail) to rely on it in a dispute.

Below, we’ll break down what an unenforceable contract is in the UK, the most common reasons it happens, and the practical steps you can take to protect your business from day one.

What Is An Unenforceable Contract (And Why Should You Care)?

An unenforceable contract is an agreement that may look valid on paper, but you can’t successfully enforce through the courts (or you can only enforce parts of it) if the other party doesn’t do what they promised.

This matters because contracts are often your first line of protection when:

• a customer refuses to pay;
• a supplier fails to deliver;
• a contractor misses deadlines or delivers poor-quality work;
• a business partner doesn’t follow through; or
• someone tries to walk away from a deal after you’ve already invested time and money.

If your agreement is unenforceable, the risk is that you’re left relying on:

• informal negotiations (which can drag on);
• a “he said, she said” factual dispute;
• limited legal remedies; or
• costly litigation with uncertain outcomes.

So while it can feel like “paperwork”, having enforceable contracts is really about protecting cashflow, relationships, and your ability to scale with confidence.

Unenforceable vs Void vs Voidable (Plain English)

These terms often get mixed up, so here’s the simple distinction:

• Unenforceable: there may be an agreement, but the court won’t enforce it (or won’t enforce certain parts) due to a legal issue like missing formalities, uncertainty, or an unfair term.
• Void: the contract is treated as if it never existed (for example, because it’s illegal).
• Voidable: the contract is valid unless and until one party takes action to set it aside (often due to misrepresentation, duress, or undue influence).

In practice, small businesses usually encounter “unenforceable” issues when a contract was rushed, copied from a template, agreed only by email without clarity, or signed without the right authority.

What Makes A Contract Unenforceable In The UK?

There isn’t one single reason a contract becomes unenforceable. Usually, it’s because the contract fails one of the legal “building blocks” of enforceability, or because a specific term is not legally acceptable.

At a high level, most enforceable contracts have:

• an offer and acceptance;
• consideration (something of value exchanged);
• an intention to create legal relations; and
• certainty of terms.

If you want a practical refresher on these foundations, it’s worth checking what makes a legally binding contract in the UK, because enforceability issues often trace back to one of these basics.

1) The Terms Are Too Vague Or Uncertain

One of the most common ways a small business ends up with an unenforceable contract is where key terms are missing or unclear.

Examples of uncertainty include:

• no clear scope of services (“marketing support” without specifying deliverables);
• unclear pricing (“we’ll agree the fee later”);
• no timeline, milestones, or completion criteria;
• no agreed payment terms (due date, invoicing process, late payment interest);
• unclear renewal or cancellation mechanics (especially in ongoing services).

In a dispute, vague drafting creates room for argument - and if the court can’t determine what the parties agreed, it may not enforce the term at all.

2) There Was No Consideration (Or The Variation Isn’t Enforceable)

In many business-to-business arrangements, “consideration” is straightforward (money in exchange for goods/services). But issues can arise when you’re trying to change a deal midstream, or when something is framed as a “promise” without a clear exchange.

For example:

• You agree to reduce a customer’s fees mid-contract but don’t receive anything in return - depending on how it’s documented and the circumstances, that change (variation) may be harder to enforce.
• You rely on a “side agreement” that was never properly documented, especially where the contract says changes must be in writing and signed.

That doesn’t mean every change is invalid - it means you should document changes properly, follow any variation clause, and consider whether a deed is more appropriate where consideration may be unclear.

3) One Party Can Challenge The Contract (Misrepresentation, Duress, Or Undue Influence)

If one party was pressured into signing, misled about key facts, or unfairly influenced, the contract is often voidable - meaning it can potentially be set aside - rather than automatically “unenforceable”. Depending on the facts and what remedies are sought, this can still prevent the contract (or certain obligations) being enforced as intended.

For businesses, the risk often shows up in situations like:

• a supplier “springing” new terms at the last moment when you have no real ability to negotiate;
• sales processes where claims are made that aren’t true (or can’t be supported);
• parties being pushed to sign without time to review or seek advice.

A good rule of thumb: if you wouldn’t feel comfortable having your negotiation emails read out loud in a dispute, it’s worth slowing down and tightening up the process.

4) The Contract Is Illegal Or Contrary To Public Policy

If the agreement involves illegal activity, the court won’t enforce it - and it may be void. This can also apply where a term is considered contrary to public policy (for example, certain overly restrictive restraints in some contexts).

Small businesses can accidentally step into this area when:

• trying to contract out of non-excludable consumer protections; or
• including clauses that attempt to remove rights the law doesn’t allow you to remove.

5) Required Formalities Weren’t Met (Writing, Signatures, Deeds)

Some agreements can be made verbally, but certain contracts either:

• must be in writing;
• must be signed in a particular way; or
• may need to be structured as a deed to avoid enforceability problems (for example, where there may be no consideration).

In day-to-day trading, the biggest “formality” risk is usually not meeting a legal technicality - it’s that the business has no clear written evidence of what was agreed, making enforcement much harder than it needs to be.

Common Clauses That Can Make A Contract Unenforceable (Or Weaken It)

Even where the overall contract is valid, particular terms can be unenforceable - which can leave your business exposed.

Here are some clauses to treat carefully.

Unfair Or Non-Compliant Consumer Terms

If you sell to consumers (not just other businesses), your terms need to work alongside UK consumer law - especially the Consumer Rights Act 2015 and the Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013.

Common issues include terms that attempt to:

• refuse refunds in circumstances where the law requires them;
• make cancellation rights unclear or misleading;
• impose disproportionate charges or penalties; or
• exclude liability for things you can’t legally exclude (like death/personal injury caused by negligence).

Even if you’re confident you’re “right”, non-compliant terms can undermine enforceability and lead to complaints, chargebacks, or regulator attention.

Overreaching Limitation Of Liability Clauses

Limitation of liability is a normal and sensible risk-management tool for small businesses - but it must be drafted carefully.

In B2B contracts, the Unfair Contract Terms Act 1977 can restrict which exclusions/limitations are allowed and requires certain clauses to be “reasonable”. If a limitation clause is too aggressive or poorly drafted, it may not be enforceable.

That’s why it’s worth properly structuring your limitation of liability terms to match your actual risk profile (what you’re providing, your fees, your insurance, and what would realistically go wrong).

“Penalty” Clauses Disguised As Fees

It’s common to include late payment fees, cancellation charges, or service credits.

But if a clause is drafted as a punishment rather than a genuine estimate of loss (or a commercially justifiable mechanism), the court may treat it as an unenforceable penalty.

Practically, the safest approach is to:

• link fees to real costs (admin time, booking loss, resourcing);
• scale fees depending on how close you are to delivery; and
• keep the clause clear and transparent.

“Agreement To Agree” Clauses

If your contract says you’ll “agree the price later” or “agree the scope later”, you might not have an enforceable deal at all.

If you genuinely don’t know the details yet, it’s often better to use:

• a clear pricing mechanism (rates, caps, bands);
• a written change control process; or
• milestones with the right to pause/terminate if not agreed.

How Can Your Business Avoid An Unenforceable Contract?

The good news is that most unenforceability problems are avoidable - if you build a repeatable contracting process and use fit-for-purpose documents.

Here are practical steps that work well for SMEs.

1) Use Properly Drafted Terms (Not Random Templates)

Templates can be a useful starting point, but they often create hidden risk when they don’t match how your business actually operates.

For example, you might copy terms that:

• don’t match your service delivery model;
• don’t deal with your main commercial risks;
• contradict what your sales team promises; or
• don’t comply with consumer rules if you sell B2C.

For many small businesses, having tailored terms and conditions is one of the simplest ways to reduce the risk of an unenforceable contract across your whole customer base.

2) Get Crystal Clear On Scope, Deliverables, And Acceptance

Clarity prevents disputes. And preventing disputes is almost always cheaper than “winning” disputes.

In your contracts, consider including:

• Scope: what you will do (and what you won’t do).
• Deliverables: what the client will receive, in what format.
• Timeline: milestones, dependencies, and what happens if the client delays.
• Acceptance: when the deliverable is treated as accepted (including deemed acceptance).
• Client responsibilities: what you need from them to do your job (content, access, approvals).

This is especially important for services businesses (marketing, software development, creative services, consultancy), where “good work” can be subjective unless you define the outputs.

3) Make Sure The Right Person Has Authority To Sign

Even a well-drafted contract can become an unenforceable contract if the person signing didn’t have authority to bind the business (or there’s a genuine dispute about authority).

To reduce risk:

• confirm the other party’s legal entity name (Ltd company name vs trading name);
• check who the directors are (for companies);
• ensure signatories are authorised (director, or someone with written authority); and
• keep a clear audit trail (emails, signing platform logs, board approvals where needed).

This matters even more for bigger deals, longer commitments, exclusivity arrangements, or where the contract includes personal guarantees.

4) Don’t “Patch” Deals With Loose Email Chains

Email contracts can be legally binding in the UK, but loose email chains are a breeding ground for uncertainty and unenforceability.

If you agree changes, put them into a clean written variation document. Depending on your setup, this might be a short addendum, deed, or formal variation letter.

In many cases, a contract amendment is the simplest way to capture changes clearly and prevent arguments later about which version applies.

5) Have A Consistent Signing Process (And Store The Evidence)

To enforce a contract, you need to prove it exists and prove what it says.

That sounds obvious - but small businesses often lose leverage because:

• the signed version can’t be found;
• attachments referenced in the contract were never attached;
• the “final” version differs between parties; or
• the quote/statement of work was updated but not re-signed.

Set up a simple internal process for: version control, signing, and storing contracts centrally (even a well-organised folder system is better than relying on inbox searches).

6) Invest In A Legal Review For High-Value Or High-Risk Deals

Not every contract needs a full legal project - but if the deal is large enough to hurt if it goes wrong, it’s worth getting it reviewed.

A focused contract review can help you spot red flags like one-sided indemnities, broken payment protections, vague scope, or termination clauses that let the other party exit without consequence (while you’re locked in).

What If You’ve Already Signed An Unenforceable Contract?

If you suspect you’ve signed an unenforceable contract, don’t panic. You often still have options - but what you do next should be strategic, because the wrong move can weaken your position.

Step 1: Identify Whether The Whole Contract Is Unenforceable Or Just A Clause

Many disputes come down to one clause (for example, a limitation of liability clause, a notice clause, or an auto-renewal clause) rather than the entire contract.

If only one part is unenforceable, the rest of the agreement may still stand.

Step 2: Check For “Entire Agreement”, Variation, And Termination Clauses

Before you rely on side emails or “what we agreed on the phone”, check whether the contract:

• claims it contains the entire agreement (limiting reliance on earlier discussions);
• requires variations to be in writing and signed; and
• sets out strict rules for serving notices or terminating.

These mechanics can determine whether you can fix the issue quickly (for example, by signing a short variation) or whether you need a more formal renegotiation.

Step 3: Consider Renegotiation Or A Replacement Agreement

If the relationship is still workable, the fastest solution is often to replace the problem contract with a clearer one.

If you’re transferring obligations to a new entity (for example, you’ve restructured, introduced a new company, or changed who is performing the service), a deed of novation may be needed to properly move rights and obligations.

Step 4: Get Advice Early (Before You Escalate)

When a dispute is brewing, it’s tempting to fire off a strong email or threaten legal action. But enforceability issues can be technical, and your communications can be used as evidence later.

Getting legal advice early helps you understand:

• what rights you actually have;
• what risks you might be accepting if you keep performing;
• how to negotiate from a position of strength; and
• what documents you should put in place to fix it.

Key Takeaways

• An unenforceable contract can leave your business without practical legal protection when a customer, supplier, or partner doesn’t follow through.
• Common causes of unenforceable contracts include vague terms, missing key deal points, missing required formalities, or clauses that fail fairness/reasonableness rules. Other issues (like misrepresentation or duress) may make a contract voidable instead.
• Even if the overall agreement is valid, certain clauses (like overreaching liability exclusions, unclear cancellation fees, or consumer non-compliance) can be unenforceable and weaken your position.
• You can reduce risk by using tailored terms, clearly defining scope and payment, confirming signing authority, documenting variations properly, and keeping clean records of signed versions.
• If you’ve already signed a risky agreement, you may be able to fix it through a written amendment, replacement contract, or (in the right scenario) a novation - but it’s best to get advice early.

If you’d like help drafting, reviewing, or fixing a contract so it’s enforceable and protects your business, you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.