How do I determine what SCCs have changed between inventory years?

These are available in the EIS (Reporting Code table) or public website:

https://sor-scc-api.epa.gov/sccwebservices/sccsearch/

Filter on “last inventory year” to remove SCCs no longer active. If this column has a date in it, then the SCC has been retired as of that date.  The “last updated date” (column J) indicates when the SCC (or other attributes such as descriptions, short names or Option Group assignments) were last updated.