H.R. 1508 would amend the definition of state of residence for purposes of the National Instant Criminal Background Check System, which would expand the types of acceptable identification a prospective buyer may use to purchase a firearm. Under current regulations, people must show identification documents with their photo and home address to the seller of a firearm as part of the background check. H.R. 1508 would allow prospective buyers to use an identification document with the address of their private mailbox or post office box if they do not have a physical residence in any state.