European social security regulations and social security conventions
When an employee works and/or lives in the Netherlands cross-border then the European regulations No 1408/71 and No 883/2004 or a social security convention will usually determine the state in which the employee is covered by social security insurance schemes. The objective of the social security regulations and social security conventions is to avoid situations in which an employee is not insured, or is insured in more than 1 state.
When the European conventions are not applicable and a social security convention has not been concluded then the national legislation of the Netherlands and the state in which the employee lives will determine which state's social security insurance schemes are applicable.
No withholding of contributions: A1/E101 certificate or declaration of applicable legislation
When a European regulation prescribes that your employee falls under the social security insurance schemes of a Member State other than the Netherlands, an EEA country or Switzerland then the employee can submit an application for an A1/E101 certificate in the state in which the employee lives. This specifies the state in which the social security insurance schemes are applicable to the employee. You will not then need to withhold and pay social security insurance contributions. The employee must apply for this certificate before starting to work in the Netherlands.
An employee who, pursuant to a social security convention, is insured in a state outside the EU, EEA or Switzerland can usually also apply for a declaration of applicable legislation. This declaration serves for the same purpose as an A1/E101 certificate.