The senator says that figures from the Joint Committee on Taxation show the bill would raise about $25 billion over the next decade.

Clearly, the government could use a few billion --- and a few trillions more --- right at the moment. Less certain, however, is the validity of Sen. Levin's argument that this difference between companies' tax returns, and their financial statements, should be changed.

"Most of the tax code doesn't align tax accounting with financial accounting," says Ed Ketz, professor of accounting at Penn State. Financial accounting tends to be accrual-based; for instance, it allows companies to book revenue before customers' funds have hit their corporate accounts. In contrast, tax accounting tends to follow a cash basis, Ketz says. Cash transactions usually are easier to measure. In addition, there's a feeling that it would be unfair, or even pose a hardship, to collect taxes on funds that are yet to be received.

What's more, an argument can be made that there's little need for the two sets of numbers to align, given that they serve different purposes. The goal of financial accounting is to give investors an accurate picture of a company's operations and performance; and the purpose of tax accounting is to provide a way for the government to obtain funds for its activities.