The correct banner marking for UNCLASSIFIED documents with CUI is:

The correct banner marking is: CUI (or CUI//<category> — e.g., CUI//SP-PRIVACY).

Explanation

• CUI (Controlled Unclassified Information) is the proper banner marking for documents that contain CUI.
• Do not use legacy banners like UNCLASSIFIED//FOUO or UNCLASSIFIED//CUI.
• Place the banner at the top and bottom of each page (and use CUI as the portion marking where appropriate).
• You may append the CUI category or markings per the CUI Registry (for example CUI//SP-PRIVACY for privacy-designated CUI).

For exact wording and required handling instructions, follow your agency’s CUI policy and the NARA CUI Marking guidance.