Every year the IRS mails millions of notices or letters to taxpayers for many reasons. For example, if IRS has a question about your tax return, changes your tax return, or needs more information from you, you will receive a notice or letter. Do not be panic, each notice deals with a specific issue and includes specific instructions on what to do. Most of the time all the taxpayer needs to do is read the notice or letter carefully and take the appropriate action.

You can find the notice (CP) or letter (LTR) number on either the top or the bottom right-hand corner of your correspondence.

Each notice or letter contains a lot of valuable information, so it is very important that you read it carefully. If IRS changed your tax return, compare the information IRS provided in the notice or letter with the information in your original return. If the taxpayer agrees, they should make notes about the corrections on their personal copy of the tax return and keep it for their records.

If your notice or letter requires a response by a specific date, you should respond as soon as possible to minimize additional interest and penalty charges and preserve your appeal rights if you do not agree.

If you do not agree with the IRS, you should mail a letter explaining why you dispute the notice. You should mail it to the address on the contact stub at the bottom of the notice. The taxpayer should include information and documents for the IRS to review when considering the dispute. The taxpayer should allow at least 30 days for the IRS to respond.

Do not forget to keep a copy of all notices or letters with your tax records. You may need these documents at a later date.

[Reference]: https://www.irs.gov/individuals/understanding-your-irs-notice-or-letter