An unlisted service code is used when?

An unlisted service code is used specifically when a service or procedure is not described by existing codes in the coding manuals. This means that when a healthcare provider performs a service that does not have a specific code assigned to it, the unlisted service code allows them to still submit a claim for that unique procedure.

Using an unlisted code both ensures that the provider can receive appropriate reimbursement and gives the payer information to evaluate the necessity and appropriateness of the service rendered. It is important for coders to provide a detailed description of the service when using an unlisted code to help the payer understand the context and justification for the procedure, as this enhances the claim's chance of being accepted and paid.

In the context of the other options, while common and well-documented procedures would have established codes, denied services usually relate to issues with claims rather than the coding itself. Similarly, a patient refusing treatment doesn't pertain to coding procedures and therefore would not lead to the use of an unlisted service code.