The CFOs at 24 large financial institutions can expect a nice little treat in the mail sometime soon from the Securities and Exchange Commission: a letter asking them for detailed information about their use of repurchase agreements and their accounting and disclosure of these transactions, Reuters reported.

The inquiry, of course, is in response to the now infamous "Repo 105" transactions uncovered at Lehman Brothers by its bankruptcy examiner, which allowed the bank to move as much as $50 billion off its balance sheet just before reporting earnings and to move them back on later.

"We are looking at the Lehman activity very, very carefully and all the issues surrounding Repo 105," SEC chairman Mary Schapiro said in an interview with CNBC on Monday.

The letters said the SEC is reviewing the firms' annual regulatory filing, or Form 10-K, and wants the firms to describe the accounting for their repurchase agreements, securities lending transactions, and other similar transactions, according to Reuters. The regulator asks for a response within 10 business days.

That's right, banks. The SEC is actually going to review your 10-Ks and the transactions that shape your balance sheets. But, in order to do that, it would be helpful if you'd point out exactly where we should be looking.

Banks shouldn't worry all that much, though. The SEC doesn't exactly have the best track record even when the red flags are laid out right in front of it. Just ask Harry Markopolos.