A very relevant article written by Kurt Marko, "Quantifying the Cost of IT Services: Accurately and Transparently Reporting IT Costs"

"managers need to start speaking the language of business, namely numbers—and they don’t mean bits, bytes, and megahertz. Yet it’s impossible for IT to provide meaningful financial figures and so-called transparency, without being able to link specific costs to IT services, and in turn, map service usage to actual business activities."

The article provides a nice overview of the need and benefits of IT Financial Management, and some useful guidance.