From the ISP website:
"On January 10, 2023, Governor JB Pritzker signed into law Public Act 102-1116, the Protect Illinois Communities Act (Act). The Act regulates the sale and distribution of assault weapons, high-capacity magazines, and switches in Illinois. The Act went into effect immediately upon signing. Individuals who possessed assault weapons, high-capacity magazines, and other devices listed in the Act before it took effect are required to submit an endorsement affidavit through their Firearm Owner’s Identification (FOID) Card account. Individuals can begin submitting their endorsement affidavits online beginning October 1, 2023. Affidavits must be submitted online through a FOID Card account. Individuals who need help submitting an endorsement affidavit can refer to the Frequently Asked Questions page or visit one of the ISP FOID Kiosks, both of which can be found on the ISP website at www.isp.illinois.gov/Home/AssaultWeapons Do not bring your weapon, ammunition, or accessories if you visit a Kiosk. A tutorial video on how to submit an endorsement affidav it through your FOID account will be available on the ISP website by October 1, 2023"