If you find a mistake on your credit report, a letter disputing the error should be your first course of action. Your credit report affects most areas of your life.It's reviewed by lenders, landlords, utility and insurance companies, and sometimes even evaluated by employers considering you for a job. Roughly 80% of reports contain errors–and 25% are serious enough to cause a denial of credit, according to a survey of 197 credit reports by the U.S. Public Interest Research Group. It's important for your dispute letter to contain the right information so your complaint can be addressed properly. Here are five keys to an effective credit report dispute letter: 1. Know what you can dispute. You have the right to dispute anything in the trade section, such as information regarding credit cards, student loans, auto and personal loans, and items in the sections for collections and public records. You may also challenge fraudulent credit inquiries and "anything that's not correct or that's outdated and only allowed to stay on your credit report for a certain period of time, such as bankruptcy,†says John Ulzheimer, president of consumer education at SmartCredit.com, a credit education website. You can't, however, dispute negative information if it is indeed correct and if it is still within the statute of limitations for reporting. For example, a Chapter 7 bankruptcy will stay on your report for 10 years; a foreclosure, for seven. 2. Consolidate disputes. To avoid lengthening the response time, consolidate all disputes in one letter; don't send a letter for each issue. Also, send the letter via certified mail, with a return receipt requested. Know what to include in your letter. 3. Keep it simple and direct. Keep it simple and direct, advises Gerri Detweiler, director of consumer education for Credit.com. Stick to the basics such as identifying information (name, address, last four digits of your Social Security number, etc.) and "a credit report reference number, which should be included in the copy of the credit report you received from the credit reporting agency.†Ulzheimer also recommends that you "clearly identify the item you disagree with, why you disagree, and what you would like to have happen.†And, he adds, send supporting documentation as needed. (Continued on next page) It's also smart to make a copy of the letter after you've signed it and keep all original copies of supporting documentation, says Sonya Smith-Valentine, who fought personal credit reporting issues in 2009 and 2010. The Largo, Maryland, resident says she wrote letters to Equifax, Experian, and TransUnion–the three major credit reporting agencies–about two matters. She says one creditor mistakenly reported her 30 days late on a payment, and a collection agency tried to collect on charges for a gym membership that didn't belong to her. There was a gym customer with Smith-Valentine's first and maiden names who also lived at an address that was similar to a previous New York address for the 43-year-old attorney. In addition to writing letters to each of the bureaus, Smith-Valentine–CEO and founder of Financially Fierce L.L.C., a consumer personal finance education company–wrote a letter to the gym. She provided a copy of her letter, as well as the gym's response, to the credit reporting companies. Smith-Valentine says the process with the credit card company involved more steps: initially calling the company to report the error, writing a letter to the office of the president of the card company when the error wasn't removed as promised, and writing the credit reporting agencies once she received a response from the president's office. She was able to share that letter with the bureaus, along with a new written appeal asking for the correction. 4. Stick to the facts. "Don't write an angry, rambling letter,†says Smith-Valentine. You're likely to get a better response if you write a polite letter that states the facts clearly. While Smith-Valentine says it took approximately four months for the credit card issue to be resolved and about three months to fix the gym error, you should expect inaccurate or incomplete information or information that can't be verified to be removed or corrected usually within 30 days, as required by the Fair Credit Reporting Act. 5. Take a two-pronged approach. File disputes with each of the major nationwide credit reporting agencies. As a second step, also submit disputes directly to the creditor or collection agency. "Disputing it directly with the source might be faster since they're required to share corrections with any credit reporting agency to which they have reported the mistake,†says Detweiler.