According to FierceGovernmentIT, one source of the the problem stems from agencies having their own definition of what falls under IT and report IT spending differently as well.
In a 58-page report published Wednesday, GAO auditors found that 26 federal agencies plan to spend almost $79 billion on IT investments in fiscal year 2011.
However, in the case of the National Oceanic and Atmospheric Administration, the agency did not report $676 million in IT-related development for two earth observation satellite systems, GAO said.
Regarding how agencies report their IT spending, OMB tells agencies to place spending in one category in order to find systems that duplicate each other. In many cases, IT investments fit in more than once category and the category itself might not be specific enough.