You must abide by Fed, State and local laws.
:
A buyer is required to show his Firearms Owner’s Identification Card (FOID) when purchasing any firearms or ammunition. Any seller is required to withhold delivery of any handgun for 72 hours, and of any rifle or shotgun for 24 hours, after the buyer and seller reach an agreement to purchase a firearm.
The waiting period does not apply to a buyer who is a dealer, law enforcement officer, or a nonresident at a gun show recognized by the Illinois Department of State Police.
The seller must retain for 10 years a record of the transfer, including a description of the firearm (including serial number), the identity of the buyer, and the buyer’s FOID number.
A federally licensed dealer must contact the Department of State Police for a background check, for which there is a $2.00 fee. Any sales at gun shows, including dealers and private parties, must contact the state police for a background check.
Private parties selling firearms at gun shows must ensure the buyer has a FOID card and the buyer must undergo a background check. It is unlawful to sell or give any handgun to a person under 18, or any firearm to a person who is not eligible to obtain a FOID.