Final answer:
In FL 59 on the UB-04 form for the patient's relationship to the insured, the correct code to indicate a child of the insured is code 19.
Step-by-step explanation:
The code used in FL 59 (Patient's Relationship to Insured) to identify a child of the insured is 19. Field Locator 59 on the Uniform Billing form (UB-04) is designated for the patient's relationship to the insured. When the patient is the child of the insured, the correct code to use is 19, which signifies a natural child, adopted child, stepchild, foster child, or ward of the insured person when the patient's relationship needs to be specified on healthcare claims.