Mistake In Contract Law In New Zealand: Types And Remedies

You’ve probably had this moment in business: a quote gets accepted, a supplier starts work, or a customer signs on - and then you spot something that’s just wrong. Maybe a price has an extra zero, the wrong entity name was used, or both sides were talking about different products without realising it.

When that happens, it’s natural to ask: “Is this contract still binding?” and “Can we fix it without ending up in a dispute?”

In New Zealand, a mistake in contract law can sometimes give you legal options - but not every error will let you unwind a deal. The law tries to balance fairness (so people aren’t trapped by genuine mistakes) against certainty (so contracts remain reliable for business).

Below, we’ll break down the most common types of mistakes, when the law may step in, and what remedies might be available - in plain English, with a small business lens.

What Does “Mistake” Mean In Contract Law?

In everyday life, a “mistake” can mean anything from a typo to a poor decision. In mistake in contract law, we’re usually talking about something more specific: a situation where a contract was entered into because one or both parties held an incorrect belief about something important to the deal.

In New Zealand, mistakes are dealt with under the Contract and Commercial Law Act 2017 (CCLA). In broad terms, the CCLA can allow a court to grant relief where a qualifying mistake is material and has caused, or would cause, a seriously unfair outcome if the contract is enforced as written. (The exact legal tests are detailed and depend on the type of mistake and the facts - so this is a high-level summary only.)

It’s also important to separate “mistake” from a few related concepts that business owners often mix up:

• Misrepresentation: someone said or implied something untrue that you relied on when entering the deal (whether intentional or innocent). See our article on misrepresentation: misrepresentation.
• Bad bargain: you agreed to a deal that later turns out to be unprofitable - that’s usually not a legal “mistake”.
• Change of circumstances: costs increase, supply chain issues happen, or demand drops after signing - that’s generally handled through the contract terms (like price adjustment clauses) rather than mistake.

If you’re unsure whether you even have a contract in the first place (because of unclear acceptance, shaky terms, or conflicting documents), it helps to start with the basics of what makes a contract legally binding.

Common Types Of Mistakes Businesses Run Into

Mistakes can show up in almost any commercial relationship - customers, suppliers, freelancers, landlords, collaborators, and even shareholders. Here are some of the most common categories we see in small business contracting.

1) Common Mistake (Both Parties Are Wrong About The Same Thing)

A “common mistake” is where both parties share the same incorrect assumption when they sign.

Example: You agree to buy a specific piece of equipment, believing it’s compliant for your intended use. The seller also believes it’s compliant. After signing, you discover a critical compliance issue that makes it unsuitable.

Common mistakes can be more compelling than “one-sided” mistakes, because neither party intended the contract to operate on the incorrect basis.

2) Mutual Mistake (You’re Each Wrong, But In Different Ways)

This is where both parties are mistaken - but not necessarily in the same way. Sometimes both sides think they’re aligned, but their understanding doesn’t match in a meaningful way.

Example: You think you’re purchasing “all branding assets” including the website and social media accounts, while the seller thinks “branding assets” only means the logo files.

These situations often overlap with poor drafting and unclear definitions, which is why getting terms properly written (and consistent across emails, quotes, and the final agreement) matters.

3) Mistake At Cross Purposes (You’re Talking About Different Things)

This is the classic “we weren’t even agreeing to the same thing” situation - both parties genuinely thought they had a deal, but the deal terms don’t line up.

Example: A customer orders “monthly support”, and you believed that meant up to 5 hours per month. They believed it meant unlimited support.

Cross-purpose problems often come from vague scope descriptions, undefined service levels, or inconsistent documents. For service businesses, a clear scope and deliverables section in a well-structured services contract can prevent headaches later.

4) Unilateral Mistake (Only One Party Is Mistaken)

A unilateral mistake is where only one party is wrong about a key aspect of the contract.

Example: You send a quote with an obvious typo (like $1,000 instead of $10,000). The other party accepts immediately and insists you honour the lower amount.

Unilateral mistakes can be harder to get relief for - especially if the other side didn’t know, and couldn’t reasonably have known, that you were mistaken. But if the mistake is obvious, or the other side “snapped up” the offer in a way that suggests they knew (or should have known) something was off, you may have options.

5) Clerical Or Administrative Errors

Some mistakes aren’t about misunderstanding - they’re about paperwork:

• wrong company name or NZBN/entity details
• incorrect address for service or delivery
• incorrect dates (e.g. start date, renewal date, notice period)
• pricing spreadsheet errors that carry into the contract
• wrong product code/SKU

These can sometimes be fixed by agreement (for example, a simple written amendment) without escalating into a full legal dispute.

When Will A Mistake Actually Give You Legal Relief?

Not every mistake lets you walk away. In commercial life, the law expects businesses to read what they sign and to run reasonable checks.

That said, under the CCLA, courts can provide relief for certain mistakes where it would be seriously unfair to hold the parties to the deal as-is.

Although each case turns on its own facts, here are practical “threshold” questions that often matter:

Is The Mistake About Something Important (Not Trivial)?

The mistake usually needs to relate to something fundamental - like price, subject matter, identity of what’s being supplied, or a key assumption that drove the deal.

Did The Mistake Cause A Significant Unfairness?

The CCLA focuses on whether enforcing the contract would be substantially unfair in the circumstances. This often overlaps with whether the mistake has led (or would lead) to a substantially unequal exchange of values.

In business terms: is one party getting a windfall or is the other party suffering a disproportionate loss because of the mistake?

Did The Contract Allocate The Risk Of This Mistake?

Many well-drafted contracts contain clauses that effectively say:

• each party has relied on its own enquiries
• no warranties are given except as stated
• the agreement is the “entire agreement”
• variations must be in writing

If the contract clearly assigns the risk to one party (or shows that party assumed the risk), it may be harder to argue you should get relief for the mistake.

Could The Other Party Reasonably Have Known?

Where one party makes an obvious error (like a wildly incorrect price), and the other party tries to take advantage of it, that context can matter.

On the flip side, if the other party honestly relied on the written terms and had no reason to suspect a mistake, a court may be reluctant to unravel the agreement.

Is This Really A “Mistake”, Or Is It A Misrepresentation/Other Issue?

This is a big one. If the problem arose because someone made a statement that wasn’t true (even unintentionally), your rights may sit under misrepresentation instead of mistake - and the remedies and strategy can be different. (It’s common for disputes to involve both arguments.)

If you’d like a more direct explainer of the legal concept, this guide on mistake of contract is a helpful starting point.

Remedies For Mistake In Contract Law (What Can You Do About It?)

If a mistake is established and the legal tests are met, the court has flexibility under the CCLA to make orders that are fair in the circumstances.

In practical terms, here are the outcomes that businesses usually care about.

1) Cancelling The Contract

In some cases, the contract may be cancelled (set aside), and the parties are put as close as possible back to where they were before.

This is often the remedy people have in mind when they say “can we get out of it?” However, cancellation under the CCLA isn’t automatic - and it isn’t the same thing as “termination for breach” under a contract. You also need to be careful about how you go about it, because purporting to cancel/terminate without a proper legal basis can create its own liability.

If you’re considering ending a deal, it’s worth understanding the mechanics of terminating a contract properly, because the notice requirements, contractual rights, and consequences can be very fact-specific.

2) Variation (Fixing The Contract Rather Than Ending It)

Sometimes the fairest outcome isn’t to scrap the agreement - it’s to correct it.

For example:

• correcting a pricing error to the intended price
• adjusting quantities to what both parties intended
• clarifying scope, deliverables, or timelines

Where the parties agree to change the contract, that can often be documented cleanly through a written amendment or Deed of Variation (especially where you want certainty and clear signing formalities).

3) Restitution Or Repayment (Undoing Benefits Already Given)

If money has been paid, services delivered, or goods supplied before the mistake is discovered, the court may order repayment or adjustments to prevent one party being unfairly enriched.

Example: You paid a deposit based on a mistaken assumption about what was being supplied. If the contract is cancelled or changed, the deposit position may need to be unwound or partially repaid.

4) Compensation-Type Orders (In Some Cases)

Depending on the nature of the mistake and the broader facts, the court can make orders to achieve a fair outcome. This can sometimes look like compensation, but it’s not the same as a straightforward “damages for breach” claim.

The key point: remedies for mistake are about fairness and correcting the consequences of the mistake - not punishing someone for breaching a contract.

5) A Commercial Resolution (Before It Becomes Legal)

In the real world, many “mistake” problems are resolved without court. A practical approach might include:

• immediately notifying the other party of the error (in writing)
• pausing performance where appropriate (without breaching)
• proposing a fair correction (e.g. updated pricing, revised scope)
• documenting the variation properly

This is where it helps to have a lawyer involved early - not just for disputes, but to keep relationships intact and get the paperwork right.

How To Prevent Costly Contract Mistakes In Your Small Business

A mistake in contract law can sometimes be fixed - but it’s almost always cheaper (and less stressful) to prevent it in the first place.

Here are practical steps that help small businesses avoid contract “blow-ups”, especially as you grow and your team gets bigger.

Use A Clear Contracting Process (Not Just Email Threads)

When you’re busy, it’s tempting to “lock it in” over email. The problem is that email chains often include inconsistent statements, old attachments, and informal approvals.

At minimum, try to standardise:

• who is authorised to issue quotes and accept terms
• which document is the “master” (e.g. signed agreement vs quote)
• how you handle purchase orders and variations
• a final check before anything is signed

If your agreements are being signed regularly (sales, suppliers, contractors), it’s usually worth investing in proper contract drafting so your documents are tailored to your business model and reduce grey areas where mistakes creep in.

Spell Out The “Commercial Basics” In Writing

Mistakes often happen because something “obvious” was never actually written down. For example:

• What exactly is being supplied?
• What is the total price and what are the payment milestones?
• What is included/excluded in scope?
• What are the delivery dates and acceptance criteria?
• Who pays for rework if requirements change?

These points can feel basic, but they’re the foundation of whether a contract is workable when something goes wrong.

Run A “Mistake Check” Before Signing

Before you sign (or send) a contract, do a quick scan for the mistakes that most commonly cause disputes:

• Correct legal names of the parties (company vs individual)
• Correct description of goods/services
• Price and tax treatment (for example, whether amounts are stated as including or excluding GST). Note: This is general information only and isn’t tax advice.
• Dates, renewal terms, and notice periods
• Limitation of liability and warranties (are they consistent with what you’re selling?)

If you’re inheriting a contract drafted by the other side, a contract review can be a smart investment - especially when the dollar value is significant or the relationship is critical to your operations.

Be Careful With Templates (Even “Good” Ones)

Templates can create a false sense of safety. Even if a template looks professional, it may:

• not match NZ law or NZ commercial practice
• allocate risk in a way that doesn’t suit your business
• create gaps where misunderstandings (and mistakes) are more likely

The aim isn’t to make contracts longer - it’s to make them clearer, so what you agreed is what you actually deliver (and get paid for).

Make Variations Easy And Documented

A lot of “mistakes” are really variations that were agreed informally - like a scope change or new price - but never properly recorded.

If your contract says “all variations must be in writing”, then relying on a casual phone call can leave you stuck later. A simple written variation process can prevent disputes and make it easier to prove what changed.

Key Takeaways

• A mistake in contract law is not the same as a bad bargain - it’s about incorrect assumptions or misunderstandings that go to the heart of the deal.
• In New Zealand, mistakes are primarily dealt with under the Contract and Commercial Law Act 2017, which can allow relief where a qualifying mistake is material and enforcement would be substantially unfair (including where it results in a substantially unequal exchange of values).
• Common mistake types include common mistake, mutual mistake, cross-purpose misunderstandings, unilateral mistake, and clerical errors.
• Possible remedies can include cancellation (setting aside), variation, and repayment/adjustments to unwind benefits already exchanged (among other orders a court considers fair).
• Not every mistake gets legal relief - factors like the seriousness of the mistake, whether the contract allocated risk, and what the other party knew (or should have known) can all matter.
• The best protection is prevention: use clear written agreements, check key terms before signing, and document variations properly.

If you’d like help reviewing a contract with a suspected mistake (or putting stronger contracts in place so issues don’t arise in the first place), you can reach us at 0800 002 184 or team@sprintlaw.co.nz for a free, no-obligations chat.