Under which circumstance would it be illegal for an NP to bill for services rendered?

Billing for services rendered by a nurse practitioner (NP) is contingent upon proper documentation of those services. When services are not documented, there is no formal record to substantiate the claim for reimbursement, which can lead to billing being considered fraudulent. Documentation serves as the evidence that the services were provided, include the specifics of the treatment or assessment, and helps verify the legitimacy of the claim. Proper documentation is also crucial for compliance with regulations set forth by insurance companies and government payers. Therefore, without documentation, it is not just an issue of potentially not getting paid; it crosses into illegal territory due to the lack of proof that services were actually provided.

Other options, while relevant in healthcare contexts, do not directly relate to the legality of billing. For example, patient refusal of treatment and lack of insurance coverage do not inherently make the billing illegal. Additionally, while following a physician's protocol is important for practice, a lack of adherence to protocols alone does not constitute illegal billing unless it leads to improper or unqualified service delivery, which would then be reflected in the documentation.