Additional work is not automatically paid work. You must be able to substantiate which additional work the client requested, why it falls outside the original assignment and how the extra price was agreed or can be justified. For construction contracts (aanneming van werk), there is also a special duty to warn of the need for a price increase.
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The best protection arises before the work is carried out: confirm the request, the extra costs and the consequences for the schedule, and obtain the approval of an authorised person. Has the work already been done and does the client refuse to pay? Then build a file for each item of additional work. A final invoice that merely lists “extra hours” is usually too little to assess the dispute properly.
When is there additional work?
Additional work consists of additions or changes compared with what was originally agreed. This may involve extra sockets, a different finish, additional designs or a new software feature. So it must first be clear what the original price and assignment covered. An unclear quotation makes it harder to show where the boundary lay.
Work needed to remedy your own failure to perform is not, as a matter of course, additional work that the client must pay for. The same applies to work that was already included in a fixed price. A time estimate that proves too optimistic does not automatically turn an agreed result into an additional assignment.
Therefore distinguish between three situations: the client asks for something extra, the original estimate turns out to be too low, or an unforeseen technical circumstance arises during performance. Different contractual and statutory rules may apply to each of these. If you label everything on the invoice as additional work, you run the risk of relying on the wrong legal basis.
Construction contracts and services are subject to different rules
A construction contract concerns the creation of a physical work. Think of a refurbishment, an installation or certain repairs. For additions or changes requested by the client, Article 7:755 of the Dutch Civil Code (BW) is relevant. That article protects the client against unexpected price increases.
Advice, marketing or other services may involve a contract for services (overeenkomst van opdracht). There, the original arrangements, any additional agreement and the rules on remuneration remain important. The special rule on additional work in construction contracts does not automatically apply to every self-employed professional who works extra hours. A mixed agreement must also be assessed carefully.
That difference is particularly relevant if you use a template that actually comes from a different sector. A construction clause may be unsuitable for a consultancy. Conversely, a general clause on hours cannot simply override the statutory protection in construction contracts. Make sure the form of contract matches what you actually deliver.
The duty to warn under a construction contract
For additions or changes requested by the client, a contractor can only claim a price increase if he pointed out the need for it in good time, unless the client should have understood that need of its own accord. That is the core of Article 7:755 of the Dutch Civil Code. Permission to change something is therefore not always permission to charge extra for it.
The warning must reach the client at a moment when it still has a meaningful choice. For example: dropping the addition, choosing a simpler design or accepting the extra costs. A notification after everything has been carried out usually does not serve that purpose. So record both the warning and the decision that follows it.
This provision cannot be excluded to the detriment of the client, save for the specific statutory exception for a standard set of conditions. A clause such as “all additional work is always payable without warning” is therefore not a safe solution. A business client can also rely on the rule on additional work.
Must the exact amount be known in advance?
It is sensible to agree a specific price or a clear method of calculation. Legally, however, a distinction must be made between warning that a price increase is necessary and providing insight into the exact amount. In HR 1 July 2022, ECLI:NL:HR:2022:989, the Supreme Court clarified the exception for a client who should have understood the need itself.
For that exception to apply, it is not additionally required that the client also had insight into the extent of the price increase. That does not mean that a contractor can then charge any amount it likes. If no amount or only an indicative price was agreed, the rule in Article 7:752 of the Dutch Civil Code on a reasonable price may apply.
The practical lesson therefore remains: discuss the costs. A clear quotation for the additional work prevents disputes about both consent and the reasonableness of the amount. If you deliberately say only that it will be “a bit more expensive”, you make a later evidential problem bigger. A price range, an hourly rate with an estimate or an agreed maximum can sometimes provide enough certainty.
An indicative price is no licence to exceed it
For construction contracts, Article 7:752 of the Dutch Civil Code contains a specific rule for an indicative price. In principle, it may not be exceeded by more than ten per cent without a timely warning of a further overrun, so that the client can limit or simplify the work. The precise arrangement determines whether an indicative price was actually given.
This is not a general rule that every business may invoice ten per cent extra without consent. With a fixed price, a contract based on hours or separate additional work, other questions may arise. A distinction must also be made between exceeding the original estimate and a new addition that the client requested later.
Where circumstances increase costs, Article 7:753 of the Dutch Civil Code may be relevant. However, an unexpected increase or incorrectly supplied information does not automatically lead to a price that can be freely adjusted. The statutory conditions and the duty to warn deserve a separate assessment. So state on the invoice why the extra costs arose and which arrangements or rules support your claim.
Who gave the additional instruction?
On business projects, you often deal with several people: an owner, project manager, site manager, architect or employee. Not everyone is authorised to enter into additional obligations on behalf of the client. Check who may approve additional work and whether a monetary limit applies. Record those authorisations at the start of the project.
A request from an employee may, in certain circumstances, still have consequences for the business, for example because of authority to represent it or justified reliance. That, however, is an assessment that depends on the facts. The title “project manager” alone is not conclusive proof that an unlimited extra budget is available.
If in doubt, send a confirmation to the authorised client: what request you received, from whom, what it will cost and that you will carry it out once approved. In urgent cases, a brief telephone consultation can come first, followed immediately by written confirmation. That is better than hoping afterwards that the final invoice will be approved without questions.
How to build the evidence for each item of additional work
Start with the original quotation, drawings, specifications and appendices. Then add the change request. Link your warning or price proposal, the approval and the evidence of performance to it. Use the same order for each item. A court or the other party must be able to follow why the item is additional without lengthy explanation.
Evidence may consist of e-mails, WhatsApp messages, job sheets, photographs, project software, timesheets and statements from those involved. Keep the full context. A stand-alone screenshot saying “fine” says little if it is not clear which proposal that reply relates to. Also note the date, sender and any attachments.
Substantiate the amount with hours, materials, agreed rates and any subcontractor costs. An internal timesheet does not automatically prove that the client ordered extra work. It can, however, support how much work was carried out. So combine evidence of the instruction, the price and the performance instead of relying on a single document.
Proof of the additional instruction does not automatically resolve every payment dispute. The client may also dispute the price, the performance or whether payment is due. For that, see disputed invoice and keep the evidence of approval, performance and invoicing separately identifiable.
What if there is only oral approval?
An oral instruction for additional work can be valid, but the evidence is more vulnerable. Who was present, what exactly was said and were messages sent afterwards confirming the arrangement? The subsequent conduct of the parties may be relevant. Think of a client who inspects the modified work or gives instructions for its execution itself.
The fact that the client benefits from the work does not in itself prove that every extra price was accepted. Nor does it automatically replace a required warning. Other legal bases can sometimes be explored, but they are not an easy way to get around missing contractual conditions.
In an existing dispute, draw up a factual chronology. Ask those involved to record their own recollection without putting words into their mouths. Keep original messages and documents. Confirmations drawn up afterwards must remain recognisable as a reconstruction; do not pretend that they were sent before the work was carried out.
Respond on the merits to a refusal to pay
First ask why the client is not paying. Is it disputing the instruction, the warning, the number of hours, the rate or the quality? Those are different disputes. Send an itemised reply to each objection and attach the key documents. A general reminder without a substantive response rarely resolves a dispute about additional work.
Separate undisputed and disputed items where possible. If the client does accept the original assignment, a dispute about a single item of additional work need not automatically block the entire settlement. Whether suspension or set-off is permitted depends on the statutory conditions and on how the items are connected. Do not assume without investigation that all withholding is unlawful.
Deal with complaints about defects separately from the price dispute. Where appropriate, offer an inspection or remedial work, with clear arrangements on access and scheduling. For a broader payment dispute, you can read more about an invoice that is disputed and not being paid for work delivered.
An example of a confirmation of additional work
A useful confirmation states: “You have requested [specific change] in addition to the work in quotation [number and date]. This change falls outside the original price. The additional price is [amount and VAT arrangement], based on [description]. The expected impact on the schedule is [consequence]. We will carry this out after your written approval.”
If a fixed price is not yet possible, describe the rate, the estimate and the moment at which you will consult again if an overrun is likely. State any uncertainties specifically. Do not use an estimate that you present as a firm maximum price when you actually intend to pass on all actual costs.
A sample text must always fit the project. For building work, other duties to warn may apply in addition to the price warning, for example regarding incorrect instructions or unsuitable materials. A single additional work form does not replace all the technical and legal obligations that come with performance.
A practical example from a refurbishment
A business owner has a shop refurbished for a fixed price. During the work, he asks for extra lighting and a relocated counter. The contractor confirms which components fall outside the quotation, sends a price and receives approval from the owner. Photographs and job sheets show the performance. If payment is refused, the instruction, price and performance can therefore each be substantiated separately.
The position is different if a fitter works extra hours without consultation because he misread the existing design. It must then first be examined whether those hours are actually for the client’s account. The same applies where an employee merely says that a different layout “would look nicer” without instructing a specific change.
These are hypothetical examples. They show why the words “additional work” on an invoice are not decisive. The facts before and during performance determine whether extra payment can be demanded. Good record-keeping makes the difference visible before the dispute escalates.
When is legal action worthwhile?
If talks have stalled, have your evidential position, the size of the amount and the prospects of recovery assessed. A well-substantiated letter of demand can help to focus the discussion. Sometimes a technical assessment is needed to distinguish original work, remedial work and additions from one another.
Do not stop other work without having your position reviewed, and do not remove delivered goods on your own initiative. Suspension, the right of retention and retention of title each have their own conditions and limits. An incorrect measure can weaken your position and cause damage. Choose a step that legally matches the specific obligation the client is failing to perform.
For proceedings, it must also be clear which court or any arbitration body has jurisdiction. Construction conditions may contain specific arrangements on this. Discuss the costs, the evidential risk and the likelihood that the other party can actually pay an amount awarded in advance. A legal claim and economically sensible debt collection are not always the same thing.
Separate the dispute about the instruction from the dispute about the amount
With additional work, two different disputes can become intertwined. The client may deny that it ordered extra work, but it may also acknowledge that it asked for it and simply consider the bill too high. So ask, for each item, which point is being disputed. A general response that “everything was already in the quotation” does not provide enough to go on for a solution on the merits.
Take as a fictional calculation six extra hours of labour at an agreed rate of €75 and €180 in extra materials, both excluding VAT. The item then amounts to €630 excluding VAT. That calculation does not yet prove that the price is payable. You must also be able to explain which change was ordered, why the hours were needed and which price arrangement or statutory basis for the price applies.
Provide a timesheet with dates and descriptions and link materials to the change. A warehouse slip without a project reference is less convincing than a proof of purchase with a clear destination. Make it visible which work was already included in the contract price, so that you do not appear to be seeking double payment.
Then request payment of the specifically substantiated, undisputed part, without unwittingly waiving the remainder. Record any partial settlement in writing. If the approval was given digitally, also look at when approval via WhatsApp can be binding. If a formal final demand is needed, use the principles for a business notice of default.
Do you work as a subcontractor? Then the contractual chain and the payment arrangements with the main contractor also play a role. Read what you can do if the main contractor does not pay.
Frequently asked questions
Can additional work be valid without a signature?
Yes, a signature is not required in every situation. Oral arrangements or digital messages can provide evidence. You must, however, be able to substantiate the additional instruction and the basis for payment. For construction contracts, the duty to warn remains relevant. Written confirmation before the work is carried out therefore reduces the risk considerably.
May I always charge ten per cent more?
No. The ten per cent rule concerns specific indicative price situations under construction contracts. It is not a general power to add a surcharge to all quotations. With a fixed price, an additional instruction or an hourly rate, it must be examined separately what the parties agreed and which statutory rules apply.
The client saw that I was doing extra work: is that enough?
Not automatically. Visible performance can be relevant evidence, but it does not always prove that the client accepted the work as an additional assignment or knew that the price would rise. Also examine the original quotation, the communication and the circumstances. An explicit confirmation remains much stronger.
What if the exact price was not known in advance?
In that case, an agreed method of calculation or a reasonable price may be relevant. Under a construction contract, the client must have been warned in good time of the need for an increase, unless the statutory exception applies. Afterwards, carefully substantiate which hours, materials and rates explain the amount.
Can I invoice additional work to make up for a quotation that was too low?
An incorrect estimate does not automatically turn originally agreed work into additional work. A price adjustment requires a contractual or statutory basis. Distinguish a change requested by the client from costs caused by your own calculation or performance.
How do I prevent new disputes about additional work?
Work with a clear scope, a list of authorisations and a fixed change procedure. For each change, confirm the work, price and schedule and keep the approval. Discuss likely overruns immediately. A simple process that is used consistently generally offers better protection than an extensive form that is only filled in afterwards.
Help with unpaid additional work
Arslan Advocaten can assess whether your claim for additional work is sufficiently substantiated and what response is appropriate. Gather the original quotation, change requests, warnings, approvals, job sheets and invoices. See our help with corporate law and business debt collection, or get in touch to discuss your file.
Written by Onur Arslan, attorney at Arslan Advocaten. Registered in the specialisation register of the Netherlands Bar for employment law and personal injury. Content reviewed on 12 September 2026 against the statutory text on wetten.overheid.nl and the judgments cited on rechtspraak.nl.
