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MARK AUSTIN THOMAS: The Supreme Court will be wrestling with a complex insurance case tomorrow. The question centers on when insurance companies have to notify you if you're paying more because of a bad credit report. Nancy Marshall Genzer explains.

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NANCY MARSHALL GENZER: Federal law says if your insurance company looks at your credit score and then decides to zap you for more money, it has to tell you.

But should that law apply to new customers? The insurers say no. Thomas Hefferon is their attorney.

THOMAS HEFFERON: Insurance companies say there's no way you could have an increase in charge if you don't have insurance with that company in the first place.

But Attorney Scott Nelson, of the group Public Citizen, takes the prospective customers' side.

The Supreme Court will be deciding whether companies intentionally broke the law. Attorney Hefferon says if insurers lose, they'll owe consumers billions.

HEFFERON: That's billions with a B like boy.

In Washington, I'm Nancy Marshall Genzer for Marketplace.