The code sets
CPT
Five-character codes for procedures and services, in three categories:
Updated annually, effective January 1. Using a deleted code produces a denial, so annual code updates are a real operational task.
HCPCS Level II
Alphanumeric codes for items CPT doesn’t cover, durable medical equipment, prosthetics, supplies, ambulance services, and drugs administered other than orally. Examples of the letter-series structure:A codes for transport and supplies, J codes for injectable drugs, E codes for durable medical equipment, G codes for temporary Medicare procedures.
ICD-10-CM
Diagnosis codes. Three to seven characters, with the structure encoding category, etiology, anatomic site, severity, and in some chapters laterality and encounter type. Updated annually, effective October 1. Code to the highest level of specificity available. RARC M81, “you are required to code to the highest level of specificity”, is a common denial driver, and unspecified codes are also a medical-necessity vulnerability. If the documentation supports laterality or encounter type, the code should carry it.CDT
Dental procedure codes, maintained by the ADA. Format isD plus four digits, organized by category of service, diagnostic, preventive, restorative, endodontics, periodontics, prosthodontics, oral surgery, orthodontics.
🦷 CDT is a separate licensed code set from CPT, used on 837D claims. A group operating both medical and dental entities needs both, and needs a clearinghouse that handles both formats. See Dental: the DSO model.
Modifiers, the common working set
Two characters appended to a CPT or HCPCS code to qualify it.
Modifiers 25, 59, and KX carry the most enforcement attention.
- 25, routinely appending it to every E/M billed with a procedure is a recognized pattern
- 59, using it to override an NCCI edit without clinical justification is unbundling
- KX, it is an attestation that policy requirements are met. Appending it without supporting documentation is asserting something you cannot prove
Revenue codes
Four-digit codes on institutional (837I) claims identifying the department or service category, room and board, pharmacy, laboratory, operating room. Maintained by the National Uniform Billing Committee. Awareness-level for most outpatient MSO-PC groups; essential if you operate a facility component.NDC
National Drug Codes identify drug products. Required on claims for many drugs, particularly by Medicaid programs, and carried alongside the HCPCS J-code with quantity and unit of measure. Format is an 11-digit number in a 5-4-2 configuration, though it appears in other configurations on packaging — converting between them is a common source of claim errors.Annual update discipline
Deleted codes deny. Both annual updates are operational tasks: update the EHR’s code sets, update charge master entries, update scrubber edits, and re-check any hard-coded code lists in your own tooling. Practices that skip an update spend the following quarter working denials that have a single root cause.