A UB-04 form is a standard billing claim form used by insurance carriers for medical claims. The form was originally developed for the Centers for Medicare and Medicaid but was adopted by other institutional providers.
Institutional providers that can use the UB-04 form for medical claims include hospitals, Native American health service facilities, rural health clinics and organ procurement organizations. The form is made up of 81 separate fields that are known as "FLs" or "form locators." Each locator is used for a specific purpose, though, as of 2014, some are not in use. FLs not in use in a UB-04 form include form locators 30 and 37.