My mother was informed by both the IRS and a tax adviser that she didn't have to file returns. TITLE TOO LONG

Consequently, since her income has been the same, she has not filed a return for a few years. I've never heard that anyone was exempt from filing a tax return and would like to know if this is true.

Yes, it is possible. Whether you have to file is a function of your taxable gross income, filing status, whether you are at least age 65, whether you are someone's dependent and whether you have self-employment income. You can find the actual filing requirements in IRS Pub 501 under the heading "Who Must File."