What Are Unenforceable Contracts in the UK?

Most small businesses don’t get stung because they didn’t have a contract. They get stung because the contract they had doesn’t do what they think it does when things go wrong.

A contract can be signed, emailed, and “agreed”… and still end up being partly (or sometimes wholly) unenforceable. That might mean you can’t rely on a key clause (like a liability cap), or you can’t force the other party to do what you expected, or you can’t recover the money you thought you were owed.

Let’s break down what “unenforceable” actually means, why it happens, and what you can do to avoid it.

First: unenforceable, void, and voidable aren’t the same thing

People use these terms interchangeably, but they’re different.

An unenforceable contract is one that exists in some sense, but you can’t enforce it in court in the way you want. Often, it’s not the whole contract that fails - it’s a particular clause (like an exclusion clause, a consumer term, or a fee clause) that doesn’t hold up.

A void contract is treated as if it never existed (in legal terms, there was never a valid deal).

A voidable contract is a contract that is valid unless and until one party takes steps to cancel it (usually because something went wrong with the way consent was obtained).

The takeaway: you can have a “real” contract and still be unable to rely on the part that matters most.

Why contracts become unenforceable (the common causes)

1) The contract is illegal or against public policy

If the agreement is for something unlawful, a court is unlikely to help either party enforce it. This can also apply where parts of the deal involve illegal performance or an illegal purpose. In practice, it’s not just “obviously criminal” contracts - it can include arrangements that try to sidestep legal obligations.

2) The contract is too unclear to apply (uncertainty)

Courts can’t enforce what they can’t understand.

If the key terms are vague, missing, or contradictory - price, scope, deliverables, timelines, acceptance criteria - you can end up with an agreement that’s impossible to apply properly.

Small business contracts often fall into this trap when they rely on a quote, a few messages, and a vague statement like “we’ll work it out as we go”. That’s fine until there’s a disagreement, and then nobody can prove what was actually included.

3) One party didn’t truly agree (problems with consent)

A contract can become unenforceable (or voidable) where the agreement wasn’t genuinely voluntary or properly informed. This can include situations involving misrepresentation (false statements that induced the contract), duress, or undue influence.

The practical issue isn’t just “was someone tricked?” It’s that even a well-written contract can unravel if the process around it was legally flawed.

4) The person signing lacked authority or capacity

In business, this usually comes up as: “They signed, but were they allowed to sign?”

If someone signs “for the company” without proper authority, you can end up chasing the wrong party - or discovering the deal was never properly binding on the company at all.

5) The contract needed a specific form (and didn’t meet it)

Some agreements are harder to enforce if they don’t follow required formalities. This comes up most often with land/property-related arrangements and guarantees.

For example, contracts for the sale or other disposition of an interest in land generally have strict writing and signing requirements (England & Wales), and guarantees are commonly required to be in writing and signed.

If you’re relying on a handshake or a loose email chain for something that usually needs more formality, you’re taking on risk.

The big one: when a clause is unenforceable even if the contract is fine

This is where most small businesses get caught out.

Your overall contract might be valid - but the clause you were relying on (to protect you) might not be enforceable.

Unfair or unclear consumer terms

If you sell to consumers, you can’t write your way out of consumer rights. Terms can be unenforceable if they’re unfair or not transparent.

And there’s a particularly sharp rule: under the Consumer Rights Act 2015, if a term (or a consumer notice) could reasonably have different meanings, the interpretation most favourable to the consumer can apply. In other words, ambiguity doesn’t just create confusion - it can legally backfire.

Unreasonable liability exclusions/limitations in B2B contracts

Even in business-to-business agreements, there are limits on how far you can exclude or restrict liability in certain situations - especially where one party is contracting on the other’s written standard terms. Under the Unfair Contract Terms Act 1977, certain exclusions or limitations may need to satisfy the reasonableness test.

And there are some hard limits too: you can’t exclude liability for death or personal injury caused by negligence, and other negligence limits must meet the law’s requirements.

This is why “standard terms” copied from the internet are risky: the clause might look strong, but it might not hold up when tested.

Penalty clauses dressed up as “fees”

If your contract includes a charge that’s really designed to punish a breach (rather than protect a genuine business interest), it may be unenforceable as a penalty.

This often shows up as dramatic “late cancellation” charges, huge “late payment” add-ons, or exit fees that aren’t connected to a legitimate interest and look out of proportion. Some charges are fine - but they have to be defensible under the modern approach to penalties.

Overreaching restraints (non-competes / non-solicits)

Clauses that go further than necessary to protect a legitimate business interest can be unenforceable. This is common in employment contracts, contractor agreements, and sale-of-business deals where a template clause is used without tailoring.

Red flags that your contract (or clause) might not be enforceable

You don’t need to be a lawyer to spot risk. These are the warning signs we see repeatedly:

• key terms are missing (scope, price, timing, deliverables, ownership)
• the contract contradicts itself (two different payment triggers, two different termination rules)
• liability clauses try to exclude “everything” in a few vague lines
• consumer terms look aggressive or unclear (especially refunds, cancellations, and “no liability” language)
• a “fee” for breach looks wildly disproportionate
• nobody can explain what the clause actually means in plain English

If you read a clause and think “I guess that’s what it means”, assume a dispute will be worse.

How to fix it (before it becomes a dispute)

If you haven’t signed yet, the best time to fix enforceability risk is now. Clean up the high-stakes clauses first: scope, payment, liability, IP ownership, termination, and dispute process. If those are clear, most problems become manageable.

If you’ve already signed, you can often reduce risk by agreeing a written variation or side letter that clarifies the fuzzy parts. The goal is to remove ambiguity before the relationship deteriorates and the ambiguity becomes leverage.

And if a dispute is brewing, get advice early. “Unenforceable” arguments can cut both ways - and you don’t want to accidentally concede something in writing that you later need to rely on.

The takeaway

An unenforceable contract usually isn’t about a missing signature. It’s about whether the agreement is legally valid, clear enough to apply, and compliant with the rules that control unfair terms, liability exclusions, and consumer protections.

If your contract is commercially important - money, risk, IP, or a long-term relationship - a review is usually far cheaper than finding out later that the protection you thought you had doesn’t hold.

If you would like a consultation on your contracts, you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.