A contractor requesting extra money after the contract is concluded because materials or wages have become more expensive needs a legal basis. Reference to inflation does not automatically make a surcharge payable. Respond specifically, request an itemised calculation and investigate the actual pricing agreement. This guide concerns Dutch construction contracts and handling a price increase request during a building project, for private and business clients.
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1. Ask the contractor to explain precisely what is becoming more expensive
Ask whether the additional bill concerns the same agreed work at higher procurement cost, a change to your instructions or an initial estimate being exceeded. These situations have different legal foundations. An item labelled additional work may actually be a materials surcharge. Request a comparison for each component of the original work, quantity, earlier price and proposed increase.
Keep the original quotation, acceptance and later messages. Record when the increase was first announced, whether materials had already been ordered and which choices remained. Respond in writing that you wish to assess the substantiation. Avoid unclear promises such as general approval of necessary extra costs. A clear information request helps address the right issue without prematurely agreeing a new price.
2. Check the pricing agreement without confusing different models
With a fixed contract sum, the agreed performance is in principle due for that amount. This differs from work charged by time and materials. For a guide price, a reasonable price applies together with statutory protection against an overrun exceeding ten percent without timely warning. A guide price does not automatically entitle the contractor to a ten-percent surcharge.
Also examine provisional sums and separate fixed component prices. A contract may combine different arrangements. Ask which part the increase concerns and why a specific rule should apply. The main question here is whether the later request fits within the existing pricing agreement or instead requires its amendment.
3. Read an indexation clause as a calculation agreement
Some contracts provide for labour and material increases or refer to an index. Ask which provision applies, which version was agreed and how the contractor applies the formula. Check the reference date, relevant index, applicable cost components and adjustment date. A general construction-cost increase does not automatically explain the same percentage on the whole contract sum, particularly where some work has already been performed.
For private clients, the consumer-law validity of a price adjustment clause must also be assessed. Unreasonable general terms may be challenged; a signature alone does not end that question. Business contracts may allocate risk differently. Have a lawyer read the clause in context, particularly where the contractor seeks both indexation and a separate extraordinary surcharge.
4. Distinguish statutory cost increases from a unilateral surcharge
Article 7:753 of the Dutch Civil Code provides, subject to conditions, a route for cost-increasing circumstances arising or becoming apparent after contract formation that are not attributable to the contractor. Relevant matters include whether the contractor should have allowed for their likelihood when setting the price. The ordinary route under paragraph 1 is a court claim for complete or partial price adjustment; a contractor’s own invoice does not replace that assessment.
There is also a special rule for cost increases caused by incorrect client-supplied data relevant to pricing, subject to a limit where the contractor should have discovered the inaccuracy. Prompt warning matters for both routes so the client can make choices about the work. Have applicable contractual departures and exact requirements checked. These provisions do not turn every disappointing estimate into the client’s risk.
5. Request evidence of cause, timing and actual effect
Ask the contractor to show old and new supplier prices, relevant order dates and quantities. Ask which part of the increase was already known or priced in at contract formation. Distinguish materials not yet ordered from fixed procurement and check whether the same increase has already been included through an index. A substantiated request identifies the financial disadvantage actually linked to the alleged new circumstance.
In ECLI:NL:RBDHA:2024:309, the court examined specifically whether price differences related to the cost-increasing circumstance invoked. Merely showing higher later quotations was insufficient for every component. Request a verifiable explanation for your own works and have the sufficiency of the data assessed. Possible savings and agreed variations also deserve their own explained place in the overview.
6. Assess warnings and unforeseen circumstances separately
A notification should still give you a real opportunity to respond to expected costs. Preserve its content as well as date: what increase was expected, for which work and which alternatives were offered? A general observation that everything is becoming more expensive need not have the same significance as a specific warning. The assessment required depends on the statutory or contractual route invoked.
Reliance on unforeseen circumstances under Article 6:258 of the Dutch Civil Code is another separate route for judicial amendment or termination under strict conditions. The issue is not merely whether something was unexpected in ordinary language, but also what the contract incorporates and who should bear the circumstances. Have the argument assessed substantively. It creates no general right to replace an agreed price unilaterally.
7. Fictional example: dearer steel without a changed design
After signing, a homeowner receives a request for additional payment for steel. The design is unchanged. The contractor calls it additional work and cites supplier price increases. The owner asks which contractual provision supports the surcharge, when procurement occurred and whether indexation was already applied. They retain the unchanged structural drawing and order messages.
The lawyer first investigates whether extra work was actually commissioned, then the pricing agreement and any statutory basis. Warning and calculation are assessed next. The parties may still discuss an equivalent construction method, but the owner first has its technical consequences checked. This fictional example does not mean every increase must be refused. It shows the information needed before payment, negotiation or reasoned dispute becomes useful.
8. Have your response and any new agreement checked
Take the contract, pricing scheme, surcharge request, substantiation and timeline to a construction lawyer. Add which activities continue, what remains unpaid and whether the contractor threatens a stoppage. Ask which response fits and how undisputed payments should be handled. Stopping all payment yourself may escalate the dispute if adequate grounds are absent. An announced construction stoppage therefore requires timely assessment.
If you agree an additional price, record precisely which work and circumstances it covers. Discuss consequences for schedule, quality, guarantees and further price requests. Also record which existing dispute is settled and which points remain open. A lawyer can formulate a workable arrangement or substantiate a challenge.
Frequently asked questions
May the contractor routinely pass inflation on to me?
No, reference to inflation alone is insufficient. The contractor must identify an applicable contractual or statutory basis and appropriate calculation. Fixed prices, guide prices and indexation agreements have different starting points.
Is a price increase the same as additional work?
No. Additional work concerns additions or changes to the appointment. Higher procurement costs for the same work require a different assessment. Ask the contractor to split the bill by cause and compare it with any variations you commissioned.
Can I simply cancel the works to avoid the surcharge?
Cancellation, termination for breach and negotiation have different financial consequences. Article 7:764 of the Dutch Civil Code and specific agreements may be relevant to cancellation, among other matters. First assess which route is available and its financial settlement, even if you dispute the increase.
Sources
These sources relate to this page. For a specific case, check current rules and your own documents.
- ACM ConsuWijzer — prijsverhoging dienstverlener Accessed: 2026-10-23
- Rechtbank Den Haag — kostenverhoging en onvoorziene omstandigheden Accessed: 2026-10-23
- Parket bij de Hoge Raad — wettelijke regeling kostenverhoging Accessed: 2026-10-23
- ACM ConsuWijzer — algemene voorwaarden Accessed: 2026-10-23
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