What action is considered ‘upcoding’ in medical billing?

Upcoding in medical billing refers to the practice of using higher codes to increase reimbursement for services rendered. This is considered unethical and fraudulent because it misrepresents the complexity and intensity of the patient's condition or the services provided. By assigning higher codes, a provider is essentially inflating the billing amount, which can lead to increased payments from insurers than what the services are actually worth or warranted.

In contrast, the other options do not align with the concept of upcoding. Applying lower codes would typically result in reduced reimbursement, rather than an increase. Delaying claim submission may create issues with timely payment or compliance but does not involve coding practices. Providing additional services without documentation does not pertain directly to coding; rather, it deals with the lack of supporting evidence for services billed. Thus, using higher codes is the distinctive characteristic of upcoding, making it the correct answer.