Before you take out a mortgage or car loan, check your credit report.

It may have a mistake that could cost you.

It’s not as uncommon as you may think. More than one-third, or 34%, of Americans found at least one error on their credit report, according to a new Consumer Reports investigation. Consumer Reports asked volunteers to get a copy of their credit report and check for errors and 5,858 did so between Feb. 1 and April 1.

Twenty-nine percent found personal information errors and 11% found account information errors.

Mistakes about personal information may not hurt your credit score, but could make it more difficult or impossible to access your credit report, said Consumer Reports policy analyst Syed Ejaz. Mistakes about account information, on the other hand, can damage your credit score.

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That three-digit number has a direct impact on your ability to get loans, such as a mortgage, and what interest rate you will pay.

“Unfortunately, sometimes folks find out way too late, when they are in the middle of getting a loan for a new house or car,” Ejaz said.

“That is why it is really important to make sure you check your credit report and assess it for accuracy.”

The Consumer Data Industry Association, which represents the major credit reporting companies Equifax, Experian and TransUnion, issued a lengthy statement in response to Consumer Reports’ findings. It called the story “completely false and misleading” and said the industry has a 98% accuracy rate.

“Accuracy is the bedrock of the credit reporting industry and getting credit reports right for consumers is our most important job,” the statement said.

Consumer Reports isn’t the only organization to report on errors. A 2012 study by the Federal Trade Commission found 25% of Americans had a mistake on their credit reports.

The best thing to do is to stay on top of your credit reports through AnnualCreditReport.com. While typically available free of charge from each reporting firm once a year, Equifax, Experian and TransUnion are offering free weekly credit reports through April 20, 2022.

If the error is about your personal information and it is preventing you from accessing your credit reports online or by telephone, write a letter directly to the reporting firms, advised Ian Lyngklip, an attorney at Lyngklip & Associates Consumer Law Center in the metropolitan Detroit area.

Make sure you include the appropriate identification, like your driver’s license, as well as proof of your address, such as a bank or utility statement. You can black out any financial information, he said.

For other mistakes, you’ll have to dispute them with each credit reporting company so that they are corrected. Clearly explain in writing what needs to be fixed and why — and provide the account number. (Here’s the FTC’s sample letter.)

Be sure to include your complete name and address, as well as the credit reporting firm’s dispute form, if it has one, and a copy of the credit report with the disputed item circled or highlighted. It’s also important to supply copies of documents that support your claim, such as credit card or bank statements, and keep records of what you send.

Notify the business, as well, and send it the same information. (Here’s the FTC’s sample letter.)

The FTC recommends sending all materials by certified mail so there is a paper trail. The credit reporting companies have about 30 days to investigate your claim. They will also forward your evidence to the business that reported the information, and it must investigate and report back.

The credit reporting company has to give you the results in writing and a free copy of your credit report if the dispute results in a change. If your dispute is not resolved, you can ask that a statement of the dispute be included in your file and in future reports.

If you lose the dispute, you can file again, but be sure to include additional information, Consumer Reports recommends. Simply resubmitting could automatically get the dispute denied.

You can file a complaint with the Consumer Financial Protection Bureau’s website if your second attempt doesn’t work, Consumer Reports advised. If the problem is severe, consider hiring an attorney who specializes in the field. You can find one through the National Association of Consumer Advocates’ website.

At the end of the day, disputing your credit report is not an easy process.

“In reality, it is really, really, really hard to fix your credit report,” said Ira Rheingold, executive director of the National Association of Consumer Advocates.

That’s because the credit reporting system wasn’t built for the benefit of consumers. It was built for the companies that use it, he explained.

“There is nothing about our credit reporting system that makes it easy for consumers, friendly to consumers or helpful to consumers,” Rheingold said.

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