Opting out of prescreened offers of credit might also be useful when you apply for a mortgage. When you seek a loan, the credit bureaus notice and they put you on a “trigger list.” The information that you are a ripe prospect is then sold to other lenders in as little time as 24 hours. Suddenly, other lenders are calling.

“It hurts the image of our members,” said Harry Dinham, president of the National Association of Mortgage Brokers. His group also objects because it could be “an avenue to identity theft.” He said, “We actually don’t know who they sell it to.”

Still, some callers may actually have better deals than the one your mortgage broker or bank is offering. “Do you want to opt out and never learn how to save money,” asked Stuart Pratt, president of the Consumer Data Industry Association, a trade group.

Will opting out protect your identity from thieves? Mr. Pratt said that “lender data tells us that prescreened offers of credit result in lower levels of fraud.” Nonetheless, he did recommend using a paper shredder on the offers you do reject.

CREDIT FREEZE The ultimate opt-out for your credit is a credit freeze. You’ll sometimes hear it recommended as a way to protect yourself from fraud because once you sign up to have your credit report frozen, no company can get access to your credit report without your expressed permission. That means no one can open up a credit card or take out a loan in your name.

Think long and hard before you do this. It sounds great at first, but doing so can backfire. You might be buying an expensive flat-screen TV at a warehouse store and want to get the instant credit card to score another 5 percent discount. You will not be able to. But about half the states have passed laws making credit reporting companies quickly unfreeze a report, some in as little as five minutes.

Not that preventing the opening of one more store account is a bad thing. Remember that everyone of those cards can hurt your credit score, which determines what your interest rate is when you borrow money.