What marking must be on a classified document when it is ready for transmission?

When a classified document is ready for transmission, it must prominently display a classification level marking. This marking indicates the specific classification category of the information contained within the document, such as Confidential, Secret, or Top Secret. Including this information is crucial for ensuring that those handling and receiving the document understand the sensitivity of its content and the necessary precautions that must be taken to protect it.

The classification level marking fulfills a vital role in maintaining security protocols and ensuring compliance with regulations regarding the handling of classified materials. It serves as a clear directive to recipients about how the information should be treated and the level of access required to view or handle the document. This clarity is especially important during transmission, where the risk of unauthorized access may be heightened.

In contrast, while tools like watermarks, security clearances, and non-disclosure statements have their purposes in security practices, they do not serve the same direct function as the classification level marking in indicating the document's sensitivity and required handling procedures during the transmission process.