No matter what the e-billing vendors say, their software primarily checks mathematics and small stuff. The software cannot make judgments about the cost of a particular task in relation to its value to the company.
While checking math, controlling fax costs, disclosing multiple time keepers at meetings, and challenging hours beyond ten billed in a day, the software is still looking through the small end of the telescope, at microbes, rather than at the universe of value received for cost.