42 CFR §424.37

1. (a)Beneficiary incapable. When a party specified in § 424.36(b) signs a claim or request for payment statement, he or she must also submit a brief statement that—
   1. (1)Describes his or her relationship to the beneficiary; and
   2. (2)Explains the circumstances that make it impractical for the beneficiary to sign the claim or statement.
2. (b)Beneficiary not present for services. When a representative of the provider, nonparticipating hospital, or supplier signs a claim or request for payment statement under § 424.36(c), he or she must explain why it was not possible to obtain the beneficiary's signature. (For example: “Patient not physically present for test.”)