When should an "add-on code" be used in coding?

An add-on code is specifically designated for use when a procedure is performed in addition to a primary procedure. This means that it enhances or adds extra detail to the primary service being billed. The purpose of add-on codes is to acknowledge the additional work done by the provider and to ensure that it is appropriately compensated in the billing process.

For instance, if a surgeon performs a primary surgical procedure and then carries out a secondary procedure that is directly related to the primary one, the add-on code corresponding to that secondary procedure should be used. Add-on codes cannot be reported independently; they must be linked to a primary procedure code. This structure helps to provide clarity in the billing process and ensures that additional services are recognized and reimbursed.

The other options do not accurately reflect the correct application of add-on codes. For instance, an add-on code does not apply to a primary service performed in isolation or for services requiring follow-up appointments, as these situations do not inherently involve additional procedures being performed concurrently or subsequently to the primary procedure.