Depending on which country you leave and which country you join, the formalities you will have to follow will not be the same.
If you stay in the Schengen area
You will not have to pay customs duties. However, border controls are not excluded. You must ensure that you do not carry dangerous or prohibited goods by customs. In addition, a certificate of change of residence may be required to authorize the transit of your personal effects in customs. This document is obtained from the local authorities or from the French consulate.
If you move out of the Schengen area
- residence abroad for more than 12 months;
- use and possession of property for more than six months prior to transfer of residence.
- an inventory of all your property detailed, estimated, dated and signed, in two copies;
- any document proving that you reside in a third country;
- any document proving that you are moving abroad.