National Incident-Based Reporting System, Volume 2: Data Submission Specifications [open pdf - 728KB]
"This document is for the use of local, state, and federal systems personnel (i.e., computer programmers, analysts, etc.) who are responsible for preparing magnetic media for submission to the FBI. It contains the data submission instructions for magnetic media, record layouts, and error-handling procedures that must be followed in submitting magnetic media to the FBI for NIBRS reporting purposes."
Federal Bureau of Investigation (FBI): http://www.fbi.gov/