Forty million Americans may have damaging errors on their credit reports, according to a new 60 Minutes expose of the nation's three main credit bureaus.

Having black marks on your files could mean denial of job offers, higher interest rates on loans, higher insurance rates, or outright denials for credit.

Disputing an error on your credit report is difficult, but it can be done. Here's what you need to keep in mind:

• File your dispute at the same time with both the credit issuer and the credit bureau.
• Do not use the automated system to dispute. Always use the manual form.
• Equifax's manual form is available here. TransUnion's manual form is available here.
• Send all documents by certified mail, return receipt requested.
• If the problem is not fixed, re-dispute it with the bureau and the credit issuers.
• If that fails, you must sue both the credit issuer and the credit bureau in small claims court. Talk to a clerk of court for guidance on the process.
• Find out where their registered agent is in the state by calling your state's corporation commission. Then serve them with the suit.
• Know that most of the time, the offenders will usually cave before the court date and remove the black mark from your report.

This requires persistence and guerrilla tactics on your part. And it's important to note that you must use the manual disputre form. Because you can send all the supporting documents in the world and the credit bureau won't pass them on when they get in touch with the credit issuer. They simply send a 3-digit code that describes the nature of your dispute to the issuer.

Remember, it is your right under the law to see your reports once each year for free through AnnualCreditReport.com.