Back in October, when news first leaked that the Department of Justice had reached a $13 billion settlement with JPMorgan Chase for the bank's role in the mortgage securities meltdown, we wrote:

"Thirteen billion dollars, $9 billion for the Treasury, $4 billion to help mortgage-holders who got hosed, sounds about right. It's the largest fine any single bank has ever been levied. You could fund the Interior Department with it, including the national parks, Fish and Wildlife, the Geologic Survey, Indian Affairs and still have a billion to play with."

It turns out that we missed the fine print, which was not entirely our fault.

The deal had been structured so that $7 billion of the settlement was tax deductible. Assuming JPMorgan pays the full corporate rate of 35 percent (which almost no corporation does), that could save the bank almost $2.5 billion.

Another $4 billion of the $13 billion was applied to a settlement the bank had reached earlier with the Federal Housing Finance Agency. Another $2 billion represented forgiveness of principle for homeowners with underwater mortgages. If that keeps homeowners from going into foreclosure, it will save the bank money in the long run. Another $2 billion involved "credits" the bank will receive on a promise to increase lending in low-income communities.

So the $13 billion settlement was really something like $6.5 billion. Lots of money to be sure, but not nearly so headline-grabbing. Plus, of course, nobody actually has to go to prison.

Last week, an odd pair of U.S. senators introduced legislation that would make it easier for the public to judge the real impact of fines levied on financial institutions. Democrat Elizabeth Warren of Massachusetts and Republican Tom Coburn of Oklahoma aimed their "Truth in Settlements Act" not just at guilty financial institutions, but at federal regulators.

Writing in the Jan. 9 edition of the New York Review of Books, U.S. District Judge Jed Rakoff suggests that accused banks and their government prosecutors often become partners in obfuscation. Judge Rakoff, who has thrown some settlements out of his Manhattan courtroom because they were too opaque, writes that overworked prosecutors often find it expeditious to cut deals with the big law firms that represent banks. Prosecutors negotiate for the biggest fine possible, but the banks get the numbers mitigated as much as possible.

That would still be possible under the Warren-Coburn bill. But at least the public would know upfront the real impact of the fines and settlements. You wouldn't need a tax lawyer and an accountant to read the fine print.

The bill would require regulators to disclose what portion of a settlement is "restitution or compensation" (deductible) and which is "penalties or fines" (taxable).

Agencies would have to post how much of the settlement included "credits" for doing the kind of business a bank normally does. For example, as Ms. Warren likes to point out, the $25 billion national mortgage settlement reached in 2012 between state attorneys general and five big mortgage-lenders included $17 billion in "credits," much of it for routine mortgage modification work.

It's always seemed patently unfair that someone who robs a bank can get prison time and be ordered to pay restitution. But a banker who rips off homeowners not only doesn't face prison, but his bank can write off big parts of the fine his actions were responsible for.

Making public the terms of punishments imposed for corporate guilt is the least that should be done. If a Massachusetts liberal and an Oklahoma conservative can agree on that, the rest of Congress should have no problem.

REPRINTED FROM THE ST. LOUIS POST-DISPATCH