First and foremost, you must respond to any IRS Notice.
If you receive a letter or notice from the IRS, it will explain the reason for the correspondence and provide specific instructions. Many of these letters and notices can be dealt with simply, without having to call or visit an IRS office.
The notice you receive covers a very specific issue about your account or tax return. Generally, the IRS will send a notice if it believes you owe additional tax, are due a larger refund, if there is a question about your tax return or a need for additional information.