I found the following on the IRS website. Call me if you have questions or want to talk more about IRS letters.
Here is what the IRS wants you to know:
Getting a letter from the IRS can make some taxpayers nervous – but there's no need to panic. The IRS sends notices and letters when it needs to ask a question about a taxpayer's tax return, let them know about a change to their account or request a payment.
When an IRS letter or notice arrives in the mail, here's what you should do:
Read the letter carefully. Most IRS letters and notices are about federal tax returns or tax accounts. Each notice deals with a specific issue and includes any steps the taxpayer needs to take. A notice may reference changes to a taxpayer's account, taxes owed, a payment request or a specific issue on a tax return. Taking prompt action could minimize additional interest and penalty charges.
Review the information. If a letter is about a changed or corrected tax return, you should review the information and compare it with the original return. If you agree, you should make notes about the corrections on your personal copy of the tax return and keep it for your records. Typically, you as a taxpayer will need to act only if you don't agree with the information, if the IRS asked for more information or if you have a balance due.
Take any requested action, including making a payment. The IRS and authorized private debt collection agencies do send letters by mail. Taxpayers can also view digital copies of select IRS notices by logging into their IRS Online Account. The IRS offers several options to help taxpayers who are struggling to pay a tax bill.
Reply only if instructed to do so. Taxpayers don't need to reply to a notice unless specifically told to do so. There is usually no need to call the IRS. If a taxpayer does need to call the IRS, they should use the number in the upper right-hand corner of the notice and have a copy of their tax return and letter.
Let the IRS know of a disputed notice. If you do not agree with the IRS, you should follow the instructions in the notice to dispute what the notice says. You should include information and documents for the IRS to review when considering the dispute.
Keep the letter or notice for their records. Taxpayers should keep notices or letters they receive from the IRS. These include adjustment notices when the IRS takes action on a taxpayer's account.Taxpayers should keep records for three years from the date they filed the tax return. Keep everything the IRS sends you.
Watch for scams. The IRS will never contact a taxpayer using social media, phone calls or text messages. The first contact from the IRS usually comes in the mail. Taxpayers who are unsure whether they owe money to the IRS can view their tax account information on IRS.gov. If someone calls you claiming to be from the IRS, it is probably a scammer. Do not send the caller any money or give them any identifying information. Ask them to write to you if they are really from the IRS.