Do you advertise in a way that is visible from the public road, for instance with billboards or illuminated signs? The municipal authority may impose advertising tax (reclamebelasting). It is irrelevant whether the advertising is above private or public land.
Conditions for advertising
You will normally need an environmental permit to advertise. Additionally, you will usually have to pay a municipal tax on encroachment on or above public land (precariobelasting) if you advertise on or above public land. This tax on encroachments on or above public land is often combined with the advertising tax in 1 tax assessment.
The rules around this tax and about what constitutes advertising may vary in different municipalities. To find out if you have to pay advertising tax and the amount, contact your municipality (in Dutch).