If you make staff available in the Dutch labour market, you will be the withholding agent for purposes of wage tax/national insurance contributions and employee insurance contributions. A withholding agent is an employer, benefits office, pension fund, etc., that has to withhold payroll taxes from the wages, benefit, pension, etc. You should register as a withholding agent with the competent tax office.
If you have no other ties with the Netherlands than making staff available, the competent office will be the tax authorities/Limburg/Department of International Issues.
If you do have other ties with the Netherlands, for instance if you have a branch, office or workshop in the Netherlands, the local tax office is competent.
Expatax can assist with the registration of your company with the tax authorities and can also assist with the formation of a subsidiary if that is prefered by you. If you only register the foreign company as a withholding agent the liability is limited to the wage tax/social security of the employee in the Netherlands. If a subsidiary is established this entity becomes fully taxable in the Netherlands, not only for wage tax but also for corporate income tax and VAT. In view of risk management it may be better to set up a subsidiary in the Netherlands but it is certainly not required.
During the waiting period a company can however run a payroll administration and pay the employees. Wage tax will be calculated too but can only be paid when the wage tax number has been provided. So this means that everything is legal.
During the waiting period the tax authorities will not provide 30% ruling declarations. This will be delayed till the moment the wage tax number is available.