You can find this guidance on pages 3 & 4 of the
MLN Evaluation and Management Services Guide:
"There are general principles of medical record documentation that are applicable to all types of medical and surgical services in all settings. While E/M services vary in several ways, such as the nature and amount of physician work required, the following general 4 Evaluation and Management Services Guide principles help ensure that medical record documentation for all E/M services is appropriate:
❖ The medical record should be complete and legible;
❖ The documentation of each patient encounter should include:
• Reason for the encounter and relevant history, physical examination
findings, and prior diagnostic test results;
• Assessment, clinical impression, or diagnosis;
• Medical plan of care; and
•
Date and legible identity of the observer."
The CMS Signature Requirements also imply that documentation must be signed before billing, but doesn't say it specifically anywhere (that I found).