Each year, the IRS sends out millions of notices to taxpayers. Some are informational only; others require a response. They can be both favorable and unfavorable. On the plus side, they may advise you of your eligibility for a tax credit; on the minus side, of a pending audit.
Notices may also alert you to an error on your tax return that triggered a refund (or a balance due). Others may request an updated address, or alert you to your eligibility for something such as the Additional Child Tax Credit. Still others will ask you to file an additional form.
In fact, there are at least 76 different form letters you can receive from the IRS on a number of topics. Check them out at www.irs.gov/Understanding Your IRS Notice.