The Commercial Register is a public register in which all businesses, legal entities and secondary establishments are recorded. The law requires that you pay a sum when you register your business in the register and following that, an annual sum, which is called the Annual Contribution. The amount depends on the capital invested in the company. The more capital that has been invested, the higher the contribution (the heaviest charges are borne by the largest companies). The law applies a total of 13 scales, starting at 80 USD and ending at 600 USD for scale 13. HERE is an overview of the scales, including the corresponding costs (in Dutch).
If you are operating as a company listed in the Commercial Register on 1 January, you are obliged to pay the Annual Contribution for that year. The Chamber of Commerce will send you an invoice in January, or by February at the latest. You must pay the invoice within 30 days; it is a statutory requirement.