What is the MINIMUM required marking for a document containing CUI?

Per DoDI 5200.48, Controlled Unclassified Information (CUI), the minimum marking requirement is that the word “CUI” must appear in the header and footer of each page of a document containing CUI. Additional markings such as portion markings or cover sheets may be applied depending on the situation, but the minimum baseline requirement is header and footer placement of " CUI " .

Reference Documents:

DoDI 5200.48,Controlled Unclassified Information (CUI)