ATF Transparency Act

Creates a new administrative appeal path and procedural protections for people denied firearm transfer or making applications, requires most such applications to be decided within three business days (otherwise treated as approved), and orders reports and a formal memorandum of understanding about how the National Instant Criminal Background Check System (NICS) is used. It also requires fee reimbursement for successful appeals and sets deadlines for federal review and interagency agreement within 180 days of enactment.