Can you report someone for not filing taxes to avoid paying back child support?

This is from the IRS website:

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. Please 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
• The estimated dollar amount of any unreported income
• Your name, address and daytime telephone number

Although you are not required to identify yourself, it is helpful to do so. Your identity can be kept confidential.

You can turn this person in but leagally you will still be responsible for back support.