The glossary to understand and take action

Multiple activity

Pursuit of several professional activities, particularly in several countries for the assessment of social security.

Notion comptable, fiscale ou juridique · Luxembourg Fiduciaries Editorial Team · Reviewed on

Understand the scope

Definition and points to distinguish

The determination of the applicable legislation depends on the activities, their status, locations and residence. It cannot be chosen based on the preferred contribution rate. A regular self-employed activity in several States must be distinguished from a temporary assignment abroad.

In your file

What this changes in practice

Multiple activity refers to carrying out activities in several situations or countries, depending on the context examined. In European social security, it requires determining the applicable legislation on the basis of all activities. The place of residence, statuses and allocation of work are factors that must be declared. One must not freely choose a scheme or consider each activity separately.

A scenario to help you understand

Educational example

A person resides in one country and works regularly in several States. They describe all their activities to the competent institution in order to have their affiliation determined.

Fictitious situation, presented to illustrate the concept.

Prepare for what comes next

Points to check

  • Déclarer toutes les activités
  • Décrire leur répartition géographique
  • Actualiser les changements de situation

The practical question

Find out more

Pourquoi déclarer également une activité exercée dans un autre pays ?

La détermination de la législation sociale peut dépendre de l’ensemble des activités, statuts et lieux de travail. Omettre une activité empêche une analyse correcte. Préparez une description complète et actualisez les changements. Les règles fiscales sur les revenus et celles de sécurité sociale sont distinctes ; une conclusion dans un domaine ne règle pas automatiquement l’autre.

Connecting concepts

Terms to know as well

Continue with the concepts, contacts and procedures related to this topic.

A1 CertificateThe A1 certificate confirms the social security legislation applicable to a person in certain situations involving European mobility.Joint Social Security Centre (CCSS)The Joint Social Security Centre (CCSS) notably manages registrations and the collection of social security contributions within its remit.Self-employed contribution assessment baseProfessional income base used to calculate the self-employed person's social security contributions.Income statementThe income statement, also called the profit and loss account in Luxembourg accounts, matches income and expenses for a period.

Put it into practice

Explore further with our guides

Practical guideSelf-employed: monitoring CCSS contributions and income changesPractical guideSelf-employed activity in several countries: preparing the affiliation assessment

Sources and verification

References consulted on 20 September 2026. Official procedures specify the applicable conditions and exceptions.

This guide explains a general process. The applicable rules depend on your situation; it does not constitute personalised advice. Report a correction.

A definition gives you a reference point. To examine your situation, clarify your question with a professional.