NICS – National Instant Criminal Background Check System:
Mandated by the Brady Handgun Violence Prevention Act of 1993 and launched by the FBI on November 30, 1998, the National Instant Criminal Background Check System (NICS) is used by Federal Firearms Licensees (FFLs) to instantly determine whether a prospective buyer is eligible to buy firearms or explosives. Before ringing up the sale, cashiers call in a check to the FBI or to other designated agencies to ensure that each customer does not have a criminal record or isn’t otherwise ineligible to make a purchase.
The following video is an overview of the NICS process: