European social security regulation No. 883/2004, social security agreements, and national legislations
When an employee works across borders, in many cases, European Regulation No. 883/2004 or a social security agreement determines in which country they are insured. The purpose of this social security regulation and the social security agreements is to prevent the employee from being uninsured or doubly insured. Separate arrangements have been made for employees working in the United Kingdom from the Netherlands or vice versa. You can find more information about this under ‘Social Security Agreements’ under ‘Brexit’.
If the European regulation does not apply and there is no social security agreement, the national legislations of the Netherlands and the country where the employee resides determine whether and, if so, where the employee is socially insured.
Not withholding contributions: A1/E101 certificate or applicable legislation statement
Employees who are socially insured in another EU country, an EEA country, or Switzerland according to the European regulation can apply for an A1/E101 certificate in the country where they reside. This certificate states in which country the employee is insured. In this case, you do not have to withhold and pay social insurance contributions in the Netherlands. The employee must apply for this certificate before starting work in the Netherlands.
An employee who is insured in a country outside the EU, EEA, or Switzerland based on a social security agreement can usually also apply for a ‘Verklaring toepasselijke wetgeving’ (Statement of Applicable Legislation). This statement serves the same purpose as an A1/E101 certificate.