Q: How should the “Gender” field be completed?
A: For item 5 - Gender
a. (Check if) Male
b. (Check if) Female
c. (Check if) Unknown
Item 5 Gender: Select options 5a Male or 5b Female if individual’s gender is known. Select option 5c “Unknown” if the individual’s gender is unknown. Leave Item 5 blank if the subject is an entity. Item 5 (Gender) does not create an obligation for a financial institution to collect this data when such collection would be in conflict with the financial institution’s obligations under any other federal law.
This is addressed in the "FinCEN Suspicious Activity Report Electronic Filing Requirements" guide, Attachment C.