@Zakia If you are referring to the value in the upper left corner of the document when you open a DocuSign Envelope then that is what is called the “Envelope ID”. It is a unique identifier for the envelope that no other envelope would have that same ID. It can be used to Search or for cases where you may need to ask DocuSign Support questions.  It is also referenced in the Envelope History and the Certificate of completion to identify that envelope.

Thanks you, it can be removed? Ou used as authentification ?

@Zakia It can be removed from the document but it would still be referenced in other places to identify the envelope such as the Certificate. It can be removed through the Advanced Options of the envelope as seen in the first article.  The second article gives more info on that Envelope ID.

https://support.docusign.com/s/document-item?bundleId=gbo1643332197980&topicId=kyt1578456367748.html&_LANG=enus

https://support.docusign.com/s/document-item?bundleId=gbo1643332197980&topicId=erv1578456367288.html&_LANG=enus