From www.IRS.gov:
Each year, the IRS sends millions of notices and letters to taxpayers for a variety of reasons. Here are ten things to know in case one shows up in your mailbox.
1. Don’t panic. You often only need to respond to take care of a notice.
2. There are many reasons why the IRS may send a letter or notice. It typically is about a specific issue on your federal tax return or tax account. A notice may tell you about changes to your account or ask you for more information. It could …