A Legible Medical Record and Authentication Matters
Medicare requires that services provided and/or ordered be authenticated by the original author. Signatures in the medical record must be clearly visible after each entry. If the signature is illegible, review contractors will accept a signature log or attestation statement to determine the identity of the author of a medical record entry. The method used must be hand-written or an electronic signature. Stamped signatures are not acceptable and if you do not have a signature log currently in place, it may be created at any time.
Resource: Medicare Program Integrity Manual, Publication 100-08, Chapter 3, Section 220.127.116.11 (PDF).