Link to original GAO report: https://www.gao.gov/products/gao-23-104719 "IRS Needs to Complete Modernization Plans and Fully Address Cloud Computing Requirements"

"The Internal Revenue Service's (IRS) legacy IT environment includes applications, software, and hardware, which are outdated but still critical to day-to-day operations. Specifically, GAO's analysis showed that about 33 percent of the applications, 23 percent of the software instances in use, and 8 percent of hardware assets were considered legacy. This includes applications ranging from 25 to 64 years in age, as well as software up to 15 versions behind the current version. As GAO has previously noted, and IRS has acknowledged, these legacy assets will continue to contribute to security risks, unmet mission needs, staffing issues, and increased costs."