Is there a phone number to call to report someone who is not filing a Federal Tax return ?

If you suspect or know of an individual or company that is not complying with the tax laws, you may report this activity by completing Form 3949-A. You may fill out Form 3949-A online, print it and mail it to: Internal Revenue Service Fresno, CA 93888. If you do not wish to use Form 3949-A, you may send a letter to the address above. Include the following information, if available: Name and address of the person you are reporting. The taxpayer identification number (social security number for an individual or employer identification number for a business) A brief description of the alleged violation, including how you became aware of or obtained the information. The years involved and the estimated dollar amount of any unreported income. Your name, address and daytime telephone number