Do you provide your customer with a warranty on the delivery that extends beyond the statutory period –

A warranty is not an extended liability for defects

This is the distinction on which this entire article stands. Liability for defects addresses whether performance was proper at the moment of handover. A warranty addresses whether the delivery maintained its promised properties for the agreed duration, even if it was without a single flaw at the moment of handover. Both can run side-by-side, and if the contract does not regulate the relationship between statutory rights and the warranty, the customer will usually assert whichever is more advantageous for them.

A quality warranty arises from a declaration by the warranty provider that they will satisfy the buyer beyond their statutory rights from defective performance if the item does not have the properties specified in the warranty statement (Section 2113 of the Civil Code under Czech legislation). The provisions on warranties apply mutatis mutandis to a warranty assumed in connection with a contract other than a purchase contract, i.e., also to a contract for work.

In its judgment 25 Cdo 295/2024 dated January 30, 2025, the Czech Supreme Court concluded that when assessing the merits of a warranty claim, it is not decisive whether the work was made without defects, but whether the work retained those properties during the warranty period that it was supposed to retain according to the contractor's declaration (the decision is available in the public database).

The case in question concerned fencing with a five-year warranty, in which the contractor undertook that the work would remain fully functional and fit for proper use throughout the warranty period and would retain the properties defined in the contract. The court interpreted this formulation as covering not only functional but also aesthetic properties, meaning that the wire should not have corroded, even though it continued to perform its protective function. The scope of a warranty is always assessed according to the purpose of the specific performance and the wording of the clause, so for production technology, normal visual wear and tear may not constitute a defect.

For suppliers, one practical rule follows from this. The sentence "the work shall retain the properties defined in the contract" is the most expensive sentence that can be written into a warranty clause. The second consequence is procedural. A customer asserting a warranty claim does not have to prove that the delivery was defective upon handover; they only need to document the content of the warranty and that the promised property disappeared during the warranty period. If the supplier wishes to defend themselves by citing an external event, they must assert and prove it themselves.

This is also why warranty disputes are won and lost on the text of the clause, not with an expert witness. An expert witness only examines what the clause has designated as a guaranteed property, not what the supplier imagined when signing.

What can be promised in a warranty without the supplier realizing it

The law adds interpretative rules to the content of the warranty that apply even if the supplier did not think of them. If the warranty provider guarantees that the item will retain its functions and performance for a certain period under normal use, it is understood that the buyer has at least the right under the warranty to the delivery of a new item without defects or to the repair of the item (Section 2114 of the Civil Code under Czech legislation). For a contract for work, the same rules apply only mutatis mutandis, and the client cannot demand a replacement work if, due to its nature, the subject of the work cannot be returned or handed over to the contractor.

The word "at least" means that limiting the warranty to repair only cannot be done by mere silence. If the supplier wants to exclude the delivery of a new item, they must explicitly state so in the declaration. The second surprise is that stating a warranty period or shelf life on the packaging of the item has the same effects. The information on the packaging is therefore not marketing, but a commitment.

The third rule targets inconsistent documentation. If the warranty declarations specify different warranty periods, the longest period applies. An offer with five years, a technical data sheet with three, and a contract with two thus default to five years. This can only be avoided if the contract explicitly supersedes previous warranty declarations and determines the order of precedence of individual documents.

The fourth rule concerns advertising. A warranty also arises from a declaration made in advertising available no later than at the time of the conclusion of the contract, and if the content of another declaration is less favorable to the buyer, the content from the advertising takes precedence. There is only one narrow exception: the advertising declaration can be modified before the conclusion of the contract in the same or a comparable manner in which the advertising was made. An amendment in the contract is not sufficient for this.

When the warranty starts running and when it gets extended

The warranty period runs from the handover of the item to the buyer; if the item was shipped under the contract, it runs from the arrival of the item at its destination (Section 2115 of the Civil Code under Czech legislation). For a contract for work, if the contractor has given a quality warranty for the work, the warranty period begins upon handover of the work. A special rule applies to deliveries commissioned by someone other than the warranty provider. There, the warranty period runs only from the date of commissioning, provided that the buyer ordered the commissioning within three weeks of takeover at the latest and provided the necessary cooperation properly and on time.

For technology suppliers, this means that the warranty can actually start months later than expected. Therefore, the clause should include an agreement on the latest deadline for commissioning. A practical solution is a dual limit. The warranty period begins on the date of commissioning, but no later than the expiry of an agreed period from takeover, typically three or six months. Although the statutory postponement assumes that the customer actually provided cooperation, a dispute over exactly that is what the clause is meant to avoid.

The same logic is required for storage. For deliveries that the customer takes over and does not install for several months, it is necessary to address storage conditions; otherwise, defects arising right there will fall under the warranty. The second extension mechanism is repair. If the contract stipulates that the warranty period is extended by the duration of the repair or that a new warranty runs for the replaced part, the period can multiply for a faulty delivery.

The third mechanism is chaining. A customer who incorporates your delivery into their own product often tries to transfer to you a warranty corresponding to their own commitment to the end customer. This is a separate negotiation, not a technical detail. In chaining, it is sensible to keep two rules. Your warranty period should not start earlier than the period the customer provides further, and it should not be longer than the period you obtain from your sub-suppliers.

At the same time, limitation periods must be distinguished from the running of the warranty period. The customer must claim the defect within the warranty period; the claim itself is then subject to the general three-year limitation period under the Civil Code, which runs from the moment the right could have been asserted for the first time. A supplier who negotiates a warranty claim for years cannot therefore be sure that the claim has expired simply because the warranty period has passed in the meantime.

When the supplier is not liable under the warranty

The statutory exclusion is single and narrow. The buyer has no right under the warranty if the defect was caused by an external event after the risk of damage to the item passed to the buyer (Section 2116 of the Civil Code under Czech legislation). However, according to the Supreme Court, the effect of the environment during the normal and anticipated use of the work cannot be considered an external circumstance. The argument that the delivery corroded due to the weather will therefore not stand on its own if it is an environment that is expected for the given use.

All other exclusions must be negotiated by the supplier themselves. These include failure to observe the prescribed service interval, intervention by an unauthorized person, use of unapproved spare parts, operation outside defined parameters, and defects caused by the substrate or subsequent performance of another supplier. An exclusion only works if it is measurable. "Incorrect operation" is weak in a dispute; "operation above 85 °C inlet temperature documented by the control unit log" is strong.

A separate category is wear parts. The scope of the warranty is governed by the content of the declaration, so without their explicit enumeration and without specifying the expected lifespan, they may fall under a generally formulated warranty period. For exclusions to work, they must be accompanied by obligations of the customer whose fulfillment can be documented. These include keeping a service log, operating within defined parameters, retaining control unit logs, and reporting third-party interventions. Without these obligations, the exclusion is a case of one word against another.

A promise that cannot be fulfilled will not save the warranty

There is a limit beyond which an overly broad promise ceases to be a commitment. The Supreme Court stated in the aforementioned case that if the contractor assumed an obligation to perform something objectively impossible under the warranty, the agreement would be invalid in that part. In practice, this means that guaranteeing a state that the given material in the given environment physically cannot achieve for the promised period is not enforceable. However, the court will not accept this defense based on mere assertion; it must be proven by expert examination.

Relying on this is therefore a bad strategy. A dispute over objective impossibility is more expensive and longer than a correctly written clause and ends with evidence gathering funded by the supplier. The opposite approach is more sensible: formulating the warranty parametrically. Instead of "it shall retain the properties defined in the contract," state specific measurable values whose maintenance the supplier guarantees, along with the measurement method.

This also resolves the most common dispute over what is still normal wear and tear and what is already a loss of a guaranteed property. In addition, the parameter gives the sales team a basis for pricing, as the measurable value can be compared with service data. Our Prague-based legal team discusses disputes over machine defects in more detail in our text How to sue for a discount due to a machine defect.

Formulations that do not belong in a warranty clause

The checklist below is based on deliveries of machines, technological systems, and construction work; for software and deliveries with regular service, the weight of individual points changes, which is why the ARROWS law firm assesses them individually for each contract. Do not use general preservation of properties without parameters. It was precisely this formulation that led to the warranty covering the aesthetic condition in the aforementioned case.

Do not use a warranty for "faultless operation" or "trouble-free run." Both are interpreted in practice as a guarantee of the result regardless of the cause. Do not use a reference to "normal lifespan" without a number. In a dispute, this is proven by an expert witness and the outcome is unpredictable. Do not use a different period in the offer than in the contract. By default, the longest of them applies, even if it was a typo in a technical data sheet that nobody read.

Do not even use a copied formulation from another supplier's contract. A wording that stood up for the delivery of a steel structure behaves completely differently for a control system, because for software, changes in properties manifest themselves differently than through physical wear and tear, and disputes are fought over functionality after environment updates. And do not use a warranty as a sales argument without calculation. Extending from two to five years changes the calculation of service reserves, not just the text of the contract.

How much a longer warranty costs and how to calculate it before making an offer

A warranty is a pricing parameter, not a legal formality, yet in offers, it is set as the last line that nobody prices. This is why the cost only shows up in the income statement of the third year, when nothing can be recharged. The basis of the calculation is the expected failure rate of the given component and the cost of one service intervention. A company usually knows both from service data; what it usually does not know is the number of interventions that will be added by extending the period, because the failure rate does not grow evenly with age.

The second item is the availability of spare parts throughout the warranty period. For deliveries with electronics, a five-year warranty is a commitment to keep a stock of parts that the manufacturer has discontinued in the meantime, or to replace them with a newer line at one's own expense. Companies underestimate this item most often. The third item is the tied capacity of the service department. A longer warranty means that technicians who should be installing new orders are traveling to handle warranty claims on old ones; for busy operations, this is an opportunity cost that is usually higher than the repair itself.

The offer should then include a reserve expressed as a percentage of the delivery price and reflected in the margin, not a footnote. If the customer demands a longer warranty and does not accept the reserve, it is a commercial decision on the price of the contract, not a concession in the text of the contract. How much of this you can bear in your offer is decided by the lifespan of the components used and whether you pass the warranty on to your customers — which is why the ARROWS law firm assesses this together with the sales team before the offer is submitted.

Before you promise a warranty in an offer

The first decision belongs to business, not law. A warranty is a cost; a longer period means a higher reserve for service, and this must be included in the offer, otherwise the company will pay for it out of profit. The second decision is about structure. A single period for the entire delivery is the simplest and most expensive option. Splitting it into structure, wear parts, and software is extra work that will pay off in the first dispute.

The third decision is about documentation. A warranty is assessed according to the text you wrote, so unifying the offer, technical data sheets, and contract is cheaper than any subsequent defense. Our Czech legal team summarizes the related context for contracts for work in our text Contract for Work in 2026. Czech companies also deliver technology abroad, and the warranty regime must then be set according to the law governing the contract.

Final summary

A longer warranty is not an extended liability for defects, but a separate commitment that is assessed according to the text of your own declaration. The article showed that what is decisive is not the quality of the delivery at the moment of handover, but whether the delivery maintained the properties you promised, and that a single generally formulated sentence can stretch the warranty even to a state that nobody anticipated.

The second half of the decision consists of money, not text. Extending the warranty period is a pricing parameter with three quantifiable items: extra repairs, holding spare parts, and tied service capacity. If they are not reflected in the offer, the company will pay for them out of the margin. For management, this implies one decision that belongs before submitting the offer, not after signing. Either the warranty is formulated parametrically, or it is given generally and the company bears a risk whose magnitude it does not know.

The cost of an incorrect wording does not manifest itself immediately, but in the third year, when the first claim arrives which, according to your ideas, was never supposed to fall under the warranty. The lawyers of the ARROWS law firm prepare and review warranty and service documentation, negotiate the scope of warranties with customers, assess them together with the sales team before submitting offers, and represent suppliers in disputes over asserted claims.

Unifying documentation and precise formulation are general principles that apply to the review of any contract — an overview of them is provided in the text on what a commercial contract review should contain.

If you want to verify what your current warranty clause actually covers, write to consultation@arws.cz or review our practice for trading and manufacturing companies.