Common Medical Billing Problems One of the most common errors in medical billing when it is handled in house at the physician’s office is a completely avoidable one. It’s called Up-coding, Undercoding, and Over-coding. Basically, correctly done coding is when the CPT-4, matches up to the correct ICD-9 or diagnosis. Sounds easy enough until you get into the sheer myriad of services available for medical billing purposes. What you need to be careful of is Up-coding that involves submitting CPT code(s) for a more extensive service or procedure than what was actually performed, or for submitting CPT codes for non-covered or non-chargeable services. Over-coding another biggie that can get your …