As soon as you are aware of the problem, do the following:
Fill out an Identity Theft Victim's Affidavit and Complaint. The Federal Trade Commission has an official identity theft form that you can use to alert or provide information to law enforcement and different companies, including the major credit bureaus, your credit card companies, your banks, and so on. You can fill out and submit or download the form at www.ftc.gov/idtheft. Make plenty of copies for yourself.
Contact the police. File a police report and keep several copies. You may need to send copies to credit bureaus, creditors, collectors, banks, and so on.
Cancel your credit cards, ATM cards, and phone cards. Notify your bank of the problem and close all existing bank accounts.
Call the credit bureaus. Ask the credit bureaus to issue a fraud alert and attach a statement to your report. Also, be sure to get copies of your credit report from each of the credit bureaus. You can ask that the reports be free-of-charge because you believe they contain inaccurate information due to fraud. (For information on ordering credit reports, see Nolo's article How to Clean Up Your Credit Report.)
Report stolen checks. Contact your bank and one or more of the major check verification companies -- request that they notify all retailers who use their databases not to accept your checks. There are many check verification companies. A few include:
Request fraud alerts from one of the three nationwide credit reporting agencies. Start with an initial fraud alert, which you can do any time. This states that you do not authorize an additional card for an existing account, an increase in the credit limit of an existing account, or new credit (other than an extension of credit on an existing credit card account). The agency receiving the alert must notify the other two agencies, and all three must place an initial alert in your file for 90 days. (Note: Because the initial alert requires creditors to take reasonable measures to confirm your identity, the alert may delay your ability to get credit.) Follow that up with a request for an extended fraud alert, which lasts seven years -- you can do this only when you've actually filed your identity theft report.
Review your Social Security earnings statement. Look for evidence that your Social Security number has been used fraudulently. Get a copy of your Social Security Earnings and Benefit Statement and look for earnings for jobs you've never had.
If someone is using your driver's license number fraudulently, obtain a new number. You should be prepared to show proof of theft and damage.
Notify the post office if you suspect the thief filed a phony change of address form. Fill out a False Change of Address Complaint, available from the U.S. Postal Inspection Service at https://postalinspectors.uspis.gov/forms/fcoa.aspx.
Take control. Most important, you need to take control of the situation and not waste time waiting for someone else to step up and help you. Vigilance is essential. Do not pay bills that you are not responsible for. Be persistent with police, credit bureaus, credit card companies, and banks. Continue to call and write letters. Keep track of your efforts to stop the theft and reverse the damage.
For more information, see Nolo's article What To Do If Your Identity Is Stolen.