Field 3, the “Patient’s Birth Date, Sex” is information that will identify the patient and it distinguishes persons with similar names.

NUCC INSTRUCTIONS: Enter the patient’s 8-digit birth date (MM | DD | YYYY). Enter an X in the correct box to indicate sex (gender) of the patient. Only one box can be marked. If sex is unknown, leave blank.

MEDICARE INSTRUCTIONS- Enter the patient's 8-digit birth date (MM | DD | CCYY) and sex.