CP2000 Notices are part of the IRS Automated Underreporter (AUR) program. A CP2000 is not an audit though procedurally they are similar. It is a proposal of additional tax, penalties and interest due to a mismatch between information returns provided by third parties to the IRS and what the taxpayer reports on a tax return. Information return examples include W-2, 1099-MISC, 1099-R, 1099-B, SSA-1099, 1099-K, 1098, etc. Taxpayers must respond to the notices in a timely fashion to dispute the proposed deficiency in order to prevent assessment and collection action.
CP2000 Reconsideration is a great way to reopen a case when you want to challenge a tax assessed during a CP2000 and you have new information or items that were not taken into account in the original CP2000. If you missed the appeals deadline, did not respond in time to a CP2000 Notice or agreed to an accuracy penalty and want to dispute it after it is assessed, CP2000 Reconsideration can be pursued.