If the 'hard-core' provisions from the applicable collective agreement are not observed, employees may still lay claim to them. To demand compliance, they may turn to the unions.
If the duty to notify is not observed, a fine may be imposed on both the employer abroad and the client. If the employer abroad or self-employed person does not observe the information obligation, a (heavy) fine may be imposed. A fine may also be imposed if the necessary documents are not available in the workplace. You can find the amounts of the fines on the Inspectorate SZW website.