An LT11 notice, also known as a 30-Day Letter, is sent by the IRS to inform you of a proposed adjustment to your tax liability. It provides you with 30 days to respond and either agree with the proposed changes or request a conference with an IRS Appeals Office. If you agree with the proposed changes, you can sign and return the included form to avoid further action. If you disagree, you should promptly file a written protest with the IRS Office of Appeals, following the instructions provided in the notice. Refer to sections §6212 and §6213 of the Internal Revenue Code for the legal basis of the 30-Day Letter. Failure to respond within the 30-day timeframe may result in the IRS automatically adjusting your tax liability.