National Instant Criminal Background Check System (NICS) Data Integrity Act of 2020 This bill modifies requirements governing the national instant criminal background check system (NICS). Specifically, it allows the NICS to retain records related to a firearms-related background check for as long as necessary to make a final determination of firearms eligibility. Additionally, it requires the NICS to query an additional database—the National Data Exchange—as part of a firearm-related background check.