The FBI NIBRS transition can be confusing since we are accustomed to SRS (Summary Reporting System). We have to now reprogram our minds to not look for Part 1 or 2 crimes but Category A or B. The FBI wants each crime to be reported per incident. This means listing out all of the NIBRS codes that pertain to an incident (without repeating the offense code more than once in an incident).
From the FBI NIBRS USER MANUAL, there are 84 UCR Offense codes, 71 in Group A and 13 in Group B. The three digit value is what you use when reporting the incident based crime in your reports.
If you would like some help matching your state or city criminal charge(s) with your what your NIBRS Offense should be, you can refer to the STATE and CITY references that have been developed. Simply look up the criminal charge and see which NIBRS code it has been mapped to.
As you enter NIBRS Offense codes you will understand how the incident based crime reporting works.