it all starts with a complaint: from dissatisfaction to action

Products or services are of poor quality, deadlines are missed or faults keep recurring. You complain, send emails, hold discussions and try to find a solution together. But when is the right time to take legal action? Is simply expressing your dissatisfaction enough to put you in a strong legal position if things really go wrong?

Supreme Court ruling of 17 July 2026

A client engaged Capgemini to rewrite an existing sports application (used by, amongst others, FC Barcelona and PSV) in a new programming language. No fixed end product or deadline had been agreed: Capgemini provided the resources and the client managed the project. Things gradually went wrong. The quality of the software fell short of expectations and the client complained extensively. At the same time, the parties continued to consult, made new agreements and carried on working as normal.

According to the Court of Appeal in The Hague, the complaints, discussions and correspondence (including a letter in which the client indicated a wish to discuss compensation and the overviews of issues, bug fixes and hotfixes that had been sent) were insufficient to justify the compensation claimed by the client.¹ In practice, the collaboration was dynamic: the parties remained in constant consultation and the work continued. From the client’s stance, Capgemini could not deduce that the client had had enough and that a firm deadline had been set for the delivery of a (modified) end product, failing which the client would take (legal) action.
The Supreme Court upheld this ruling.²  The Court of Appeal had made the correct assessment: in a dynamic collaboration without a fixed end product, one cannot simply assume that the other party will understand from ongoing complaints that the client has had enough.

The key message of the judgement is that, particularly in projects without a clearly defined end product and without fixed deadlines, building a solid case file is especially important and requires careful and consistent action. It also underlines the importance of considering deliverables, KPIs and timing in advance.

Explaining the difference: lodging a complaint vs. giving notice of default

A complaint and a notice of default are not the same thing. A complaint makes it clear that you are dissatisfied with a performance. A notice of default goes a step further and serves a completely different purpose: it provides the other party with a formal, written warning, informing them that they have one final opportunity to rectify the situation within a specified timeframe, and that legal action will be taken if the issue is not resolved or the obligation fulfilled in a timely manner. The notice of default must be clear about exactly what is required of the debtor, and within what timeframe. A message that merely lists all the issues is therefore not necessarily sufficient. Particularly if the parties continue to consult and cooperate in the meantime, it may remain unclear exactly what is required of the other party and when a breach occurs.

What can you do in practice?

Are you dissatisfied with the other party’s performance? In that case, do not just send a complaint, but also set out the following in writing:
1. which obligation is not being fulfilled, or is not being fulfilled properly;
2. what specific performance you expect from the other party;
3. within what reasonable timeframe rectification or performance must take place; and,
4. what consequences you attach to a failure to fulfil the obligation.

If rectification or performance subsequently fails to materialise, take action and do not continue as before. This will prevent any subsequent dispute over whether your warnings were clear enough. A proper notice of default is not a mere formality. It can make the difference between being right and being proved right.

Are you unsure about your position or the next steps you should take? We’d be happy to help you work through this.

¹ Court of Appeal, The Hague, 14 January 2025, ECLI:NL:GHDHA:2025:10. 
² Supreme Court, 17 July 2026, ECLI:NL:HR:2026:1295.