The ICD-9-CM is used for diagnostic coding in the United States. ICD-9 codes are required for reporting patients' conditions on health-care claims. Codes are made up of three, four, or five numbers and a description. New codes are issued annually, and current codes should be used because they can affect billing and reimbursement.

The ICD-9 has two volumes that are used in medical practices: the Tabular List (Volume 1) and the Alphabetic Index (Volume 2). To find a code, use the Alphabetic Index first. Its main terms may be followed by related terms. The codes themselves are organized into 17 chapters and are listed in numerical order in the Tabular List. Code categories consist of three-digit groupings of a single disease or a related condition. Further clinical detail is shown by four- or five-digit codes. The conventions used in the ICD-9 must be observed to correctly select codes.

V codes identify encounters for reasons other than illness or injury and are used for healthy patients receiving routine services, for therapeutic encounters, for a problem that is not currently affecting the patient's condition, and for preoperative evaluations. E codes, which are never used as primary codes, classify the injuries resulting from various environmental events.

CPT provides a standardized list of five-digit procedure codes for medical, surgical, and diagnostic services. Add-on codes and modifiers may also be selected.

CPT is divided into six sections: (1) evaluation and management, (2) anesthesiology, (3) surgery, (4) radiology, (5) pathology and laboratory, and (6) medicine. The three main factors that influence the level of service for coding purposes are the type and extent of (1) history, (2) examination, and (3) medical decision making. Surgical packages and laboratory panels should be coded as single procedures rather than broken into component parts.

The Health Care Common Procedure Coding System (HCPCS), used to code Medicare services, has codes from CPT as well as Level II national codes.

Diagnoses and procedures must be correctly linked when services are reported for reimbursement because payers analyze this connection to determine the medical necessity of the charges. Correct claims also comply with all applicable regulations and requirements. Codes should be appropriate and documented as well as compliant with each payer's rules.

A medical practice compliance plan addresses compliance concerns of government and private payers. Furthermore, having a formal process in place is a sign that the practice has made a good-faith effort to achieve compliance in coding.