A credit reporting error could affect your credit score and how much you pay for credit when you apply for a loan for a major purchase such a house or a car, or a credit card. That’s why it’s important to monitor and maintain a report free of errors. Depending on the nature of the errors, your credit scores could take a significant hit if they aren’t corrected. They can also make you more susceptible to identity theft if the wrong person gets ahold of your name, Social Security number or credit card number. (You can see how credit report errors are affecting your credit by viewing a free snapshot of your credit report on Credit.com.)

According to the Fair Credit Reporting Act, both the credit reporting agency and the lender providing the inaccurate information are responsible for correcting the error. Here are some other important tips for correcting errors on your credit report.

How Can I Dispute Errors on My Credit Report?

First things first, you’ll want to put your dispute in writing. In your dispute letter to a credit reporting agency, be sure to clearly explain why the item on your credit report is not accurate and request that the item be removed from your credit report. It’s a good idea to include copies of supporting documents — don’t send the originals! As the Federal Trade Commission notes on its website, “you may want to enclose a copy of your report with the items in question circled.” Be sure to provide your full name and address as well.

We advise sending the letter by certified mail with a return receipt so you know when the credit reporting agency has received it. In most cases, a credit reporting agency will investigate your complaint within 30 days, unless they find it “frivolous,” the FTC notes. You can also send a similar dispute letter to the creditor supplying inaccurate information to the credit reporting agency. Again, be sure to keep the original copies on file.

How Does a Credit Dispute Investigation Work?

Once a credit agency begins investigating your dispute, they “must forward all the relevant data you provide about the inaccuracy to the organization that provided the information,” the FTC says. After the company receives a notice of dispute from the credit reporting agency, it must investigate and report its findings back to the credit reporting agency. “If the information provider finds the disputed information is inaccurate,” the FTC says, “it must notify all three nationwide credit reporting companies so they can correct the information in your file.”

When the investigation has wrapped, a credit reporting agency is obliged to send you the results in writing as well as a free copy of your credit report if a change has been made. Note: This credit report does not count as your annual free credit report, the FTC says. What’s more, the credit reporting agency is forbidden from putting the disputed information back in your file unless it has been verified. The credit reporting agency will send you a written notice including the name, address and phone number of the organization that provided the information.

What Can I Do if the Error Is Not Corrected?

Remember, your credit file doesn’t always reflect everything in your credit accounts. Not all creditors furnish information to the credit reporting agencies, and these include travel, entertainment and gas card companies, according to the FTC. So it’s important to keep an eye on all three versions of your credit reports to make sure your information is up-to-date and reported accurately.

If the error on your credit report is not corrected, you can request to have a statement of dispute be included in your credit file. You can also file complaints with the Consumer Financial Protection Bureau, the Better Business Bureau and the office of the Attorney General in your state about the credit reporting agency and the company furnishing inaccurate information. Finally, you may wish to consult a consumer attorney about your legal rights.

This article has been updated. It was originally published August 13, 2014.