Disputing a contractor’s extra-work bill: when is legal help useful?

1. Establish the original scope of work

Start with the quotation and accepted specification. Which work and materials were included, and what was expressly excluded? Keep drawings, selections and messages confirming your agreement. Without this starting point, it is unclear whether an item genuinely represents additional work or was already included in the contracted job.

List the disputed items. For each one, record the original agreement and the document showing it. Use the invoice’s description and identify the difference in scope or price. A general statement that the bill is too high makes it difficult for an adviser to identify which agreement requires interpretation.

2. Distinguish a fixed price, an estimate and time-and-materials pricing

ConsuWijzer distinguishes a fixed total price, a guide price and payment based on hours and materials. A guide price is an estimate; a fixed price allocates the risk of difficulties differently. Read the actual agreement instead of relying solely on the heading “quotation”.

For time-and-materials work, establish the agreed rates, material charges and any limits. Ask how the final price was calculated. A difference between a budget and the invoice does not by itself establish that the same rules apply as for a fixed price. Several documents may together establish the pricing agreement; have ambiguous combinations assessed.

3. Did you change the instructions?

If you request a different finish or extra work during construction, this may create additional work. ConsuWijzer highlights the need for a timely warning about higher costs. It also describes exceptions, for example if you should have understood that your new wishes would cost more or if a separate agreement was made for the additional work.

Do not merely note that you never signed a separate form. Gather what was discussed verbally and in writing, who requested the change and how the contractor responded. Distinguish an enquiry about possibilities from an actual instruction. That distinction may matter when interpreting conversations on site.

4. Assess an increase above a guide price carefully

For a guide price, ConsuWijzer explains that without the required timely warning the price generally may not rise by more than ten percent. A warning must leave room to make decisions about the work. Ten percent is therefore not a universal supplement applicable to every fixed-price job or change of instructions.

Check when the warning arrived and what could still be adjusted. Keep messages with specific amounts and the replies. Before calculating an increase, establish which scope and price belong in the comparison. Separately agreed additional work may present a different question from exceeding the guide price for the same work.

5. Separate unexpected difficulties from incorrect information

Not every extra hour results from a new request. The contractor may cite more expensive materials, a more difficult job or incorrect information. Ask what caused each charge and which agreement supports the increase. This prevents different types of price differences from being treated as one issue.

ConsuWijzer also discusses the skilled contractor’s role when a customer provides incorrect or incomplete information. Whether that information should have been checked depends on the circumstances. Give your adviser both your original information and the contractor’s questions or warnings. Do not assume that every incorrect measurement must always be paid for by the same party.

6. Challenge the invoice precisely and choose your next step

Write down which items you dispute, why and what supporting detail you request. Identify the original agreement on which you rely. ConsuWijzer provides a model letter for disputing additional work under a fixed-price agreement. Adapt any model to your own pricing arrangement and facts; the wrong model can obscure the real complaint.

For a substantial dispute, also obtain advice about payment, continued work and any debt-collection letter. Disputing a few items does not automatically answer the question of the entire final account. Show disputed and undisputed amounts separately, and seek advice before taking a major step.

7. Fictional example: different tiles and an unexpected substrate

Suppose a consumer agrees a fixed price for a bathroom, then chooses a more elaborate tile pattern. The final invoice includes both that pattern and additional costs arising from an unexpectedly difficult substrate. The customer finds both charges surprising, but their causes differ.

A useful preparation is to collect the instruction change, warning and pricing agreement for each item. The tile-pattern choice is then not automatically treated in the same way as the risk associated with the substrate. This fictional example does not determine what is payable; it shows why an itemised file is needed.

8. Checklist for a construction lawyer consultation

Put the extra amount claimed and current state of the work at the top of your file. Flag a specific deadline, collection threat or announced work suspension. First ask for an assessment of the scope and pricing basis, then agree which letter or procedure is necessary.

• Accepted quotation, specification, drawings and terms.
• Agreements about a fixed price, guide price, hourly rates and materials.
• Requests for changes and warnings, with dates and responses.
• Itemised extra-work invoice and a list of disputed charges.
• Payment records, your written objection and any collection documents.