While the activities making up this last mile may have been among the last to be automated, that's steadily changing, Pritchard says. Many CFOs he's talked with now rank such an overhaul as among the top five projects on their to-do lists. They recognize that their organizations are missing opportunities for time- and cost-savings, and that they take on risk if they lack visibility and control into these processes, he adds.

For that reason, some experts advise against outsourcing such operations. "You're literally signing the document that could put you in jail," according to Colbert. "You have to own the process."

Effectively automating at that late stage requires a holistic approach that encompasses people, data, best-practice processes and technology, Pritchard says.

The Oneida Nation's Fetterman recommends mapping a detailed calendar of all activities that currently make up the last mile, and identifying those that can reasonably completed earlier. For instance, it may be possible to set an earlier deadline for the accounts payable group, even if not all bills have entered the system, and then accrue any that remain, if material.