Secretly Building Stands for Your Employer’s Client? This Project Manager Now Owes €200.000

A project manager at a Dutch stand-building company spent part of his employment quietly running jobs for one of his employer’s own clients – an American company whose account he managed.

It ended with summary dismissal, and this month it ended a second time: the cantonal court in Noord-Holland ordered him to pay his former employer €198.859,11 in damages, mostly for the profit the company lost on projects that should have been theirs.

The ruling (Rechtbank Noord-Holland, 5 August 2026, ECLI:NL:RBNHO:2026:9867) is worth ten minutes of any event professional’s time. Not because the law is new, it isn’t, but because it shows, in unusually concrete numbers, what moonlighting for a client actually costs when it comes out. And in this industry, it tends to come out.

What happened

The project manager had been with the company since December 2012. His contract contained both a non-compete clause and a side-activities clause: during employment, no work for any other employer or client, and no business for his own account. As project manager, he handled relationship management for several clients, including the American company.

In March 2025, a colleague tipped off the employer: the project manager was building an exhibition stand during working hours for a client that had no order running with the company. He had asked the colleague to help with the build, and to keep quiet about it.

The employer had an IT supplier read out the data from his business laptop. Confronted with what it contained, the project manager admitted the side work and acknowledged he had been, in his own words, walking a thin line. He was dismissed on the spot, in the same meeting.

The defence that didn’t work

In court, the ex-employee argued that the side-activities clause “wasn’t top of mind”, that it had come to weigh more heavily as his role grew, and that Dutch law on side-activity clauses changed on 1 August 2022 – since then, employers need an objective justification to enforce a ban on side jobs.

The court dismissed all of it. Growth in the role and the change in the law did not invalidate the clause. More importantly, the judge added that even without any clause, this conduct would still have been impermissible: secretly competing with your own employer, for your employer’s own client, breaches the basic duty to behave as a good employee. The clause made the case easier to bring, but it was not what made the conduct wrong.

The court also rejected the idea that summary dismissal was punishment enough. Being fired for the conduct does not prevent the employer from separately recovering damages.

The bill

The damages break down as follows: €188.000 in lost profit on three projects the employee acknowledged doing, €3.344,82 in lost supplier discount points, €5.335 in fixed statutory compensation, and €8.554,50 in costs for establishing the damage – €205.224,32 in total, of which €6,365.21 had already been offset against his final pay. Regarding the lost profit, the employee argued he had been paid far less for the three projects than the employer claimed it had missed. The court was unmoved: what matters is the profit the employer would have made on those jobs, not what the employee pocketed.

That distinction should give pause to anyone tempted by side work. A freelance job that earns you a few thousand euros can create a liability measured in your employer’s margin on the same work, a much bigger number, in an industry where a single stand project can carry serious value.