Front page marking: If a document contains UCNI (and no classified or OUO information), the front page must have the front marking. (§ 1017.16 (a)(1)).
Page marking: The marking "Unclassified Controlled Nuclear Information" must be placed on the bottom of the front of the document and on the bottom of each interior page of the document that contains text or if more convenient, on the bottom of only those interior pages that contain UCNI. The page marking must also be placed on the back of the last page. If space limitations do not allow for use of the full page marking, the acronym ''UCNI'' may be used as the page marking. (§ 1017.16 (a)(2)).
Transmittals: A document that transmits documents or material marked as containing UCNI and does not itself contain classified information or UCNI must be marked on its front with "Document(s) transmitted contain(s) Unclassified Controlled Nuclear Information. When separated from enclosures, this transmittal document does not contain UCNI." (DOE O 471.1B, 4h(4)).
Marking Material: If possible, material containing or revealing UCNI must be marked as described in § 1017.16(a)(1). If space limitations do not allow for use of the full marking in § 1017.16(a)(1), the acronym "UCNI" may be used. (§ 1017.16 (a)(4)(b)).
Marking e-mail: An e-mail message that contains UCNI must be marked as follows (DOE O 471.1B 4h(5)):
The first line of an e-mail message containing UCNI must include the abbreviation "UCNI," the Reviewing Official's name and organization, and the guidance used to make the UCNI determination (e.g., UCNI; Jane Smith, HS-90; CG-SS-4). If there is an attachment that contains UCNI, it must have all required UCNI markings.
If the message itself is not UCNI but an attachment contains UCNI, the message must indicate that the attachment is UCNI. The attachment must have all required UCNI markings.
Examples of the above markings and other examples are provided in the UCNI Marking Reference. .
Marking requirements are detailed in 10 CFR 1017.16 and DOE O 471.1B, 4h.