What Is an SO Number in the Prison System?

SO number stands for Sex Offender number. It is an identification number assigned to individuals who have been convicted of a sex offense and are required to register under their state's sex offender registry.

The SO number is separate from an inmate's prison ID number. It is the identifier used by law enforcement and registry systems to track registered sex offenders, and it stays with the individual after release as long as they remain on the registry.

If you are trying to locate someone in the system and have an SO number, it can be used to search state sex offender registries directly. Most states maintain public-facing registry search tools through their department of public safety or attorney general's office.