How many diagnosis codes does UB-04 generally support, and what is their order?

• A. It allows multiple diagnosis codes; the principal diagnosis is listed first, followed by other diagnoses up to the payer’s limit (commonly up to 12).
• B. Only one diagnosis code is used.
• C. Diagnosis codes are listed in reverse order.
• D. Diagnosis codes are not used for UB-04.

Answer: (A)

UB-04 supports more than one diagnosis code, and the order matters. The principal diagnosis—the main condition that led to admission or the primary reason for the encounter—is placed first. After that, additional diagnoses that are relevant to the patient’s stay, such as other active diseases, comorbidities, or complications, are listed in order of importance up to the payer’s limit. On most UB-04 claims, you can include up to 12 diagnosis codes in total, with the principal diagnosis occupying the first position and the rest filling the subsequent slots. This structure helps with accurate DRG assignment and reimbursement, since the principal diagnosis drives the main payment category while secondary diagnoses reflect additional factors that influence resource use. Some payers may have different maximums, but the common practice is to list multiple codes beginning with the principal diagnosis, then the others up to the limit.