If you (are starting to) work in the Netherlands, you may want to enroll in employment with the Dutch Employer of Record.
Invoicing for your services is also an option, but only allowed if your #1 customer accounts for a max of 70% of your income, and you should have 2 additional customers that account for at least 10% each.
If you (are starting to) work for 1 client exclusively, enrolling with the Dutch Employer of Record may be a good option. It saves you from registering with the Dutch tax authority and automatically covers you for employee insurance. (paid leave, sick pay, etc..). We’ll calculate the applicable fees and make sure all taxes are paid. We’ll save your clients the hassle of permanent establishment and the risk of misclassification.