I henhold til forordning nr. 3, artikel 12, forbydes det andre medlemsstater end den, på hvis territorium arbejdstageren er beskæftiget, at lade denne være omfattet af deres lovgivning om social sikring, når noget sådant vil medføre forøgede byrder for arbejdstagerne eller arbejdsgiverne, der ikke modsvarer en yderligere social beskyttelse.
Article 12 of Regulation No 3 prohibits a Member State other than that in whose territory a worker is employed from applying its social security legislation to such worker where to do so would lead to an increase in the charges born by wage­earners or their employers, without any corresponding supplementary protection by way of social security;