Commission on Dormant Assetsassets.publishing.service.gov.uk › attachment_data › filePDF
potentially dormant financial and non-financial assets. Its ambition ... Where it is not possible to reunite dormant assets with their rightful owners, there ... liquidity of the assets. More

These are accounts that have never been claimed (and those that have no legal person to inherit them). They must be treated a certain way under law.

The information states that after ten years the bank must register the client's savings accounts or assets in a base of centralized donations and that the bank must manage them as non-contact accounts. After another delay of fifty years the assets are disinherited and, in formal terms can be transferred to the confederation of the preserved rights of clients and their successors until transfer to the confederation.
"La Banque, après dix ans, est tenue d'enregistrer les avoirs du client dans une base de données centralisées et de les gérer comme avoirs sans contact. Après un nouveau délai de cinquante ans les avoirs en déshérence donnent lieu à une publication, et, au terme de ces formalités, les actifs sont transférés à la Confédération les droits des Clients et de leurs successeeurs préservés jusqu'au transfer à la Confédération."

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Note added at 4 days (2020-07-02 23:10:29 GMT)
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A confederation is an organisation which consists of a number of groups united in an alliance or league, for instance ' a confederation of trade unions'. In the words of the source text "les actifs sont transférés à la Confédération" describes asset values which are transferred (passed along) to an organisation. The words of the source text " les droits des clients et de leurs successeurs préservés" tells that the rights of clients and those who follow are preserved (protected). The bank might not use the term 'non-contact accounts' but it's about customers' finances being organised without face to face negotiation (by phone, letter or internet). It can also be about on line banking or internet banking, which might be more important now.