what marking banner and footer acronym at a minimum is required on a dod document

The minimum marking acronym required on a DoD document containing controlled unclassified information is CUI.

Quick answer

For a DoD document with CUI, the banner and footer must at minimum use “CUI” at the top and bottom of the page.

Why

DoD guidance says the required minimum marking for unclassified DoD documents containing CUI is the acronym CUI in the banner and footer, and it does not require adding “U” to the banner/footer. A DoD CUI marking aid also states that the mandatory minimum marking is CUI banner/footer markings.

If you want, I can also give you the exact wording for the full CUI marking block.