A more thorough explanation:

A revenue agent's report is a document that shows any changes made to a tax return after an audit by the Internal Revenue Service (IRS). The report is sent to the taxpayer along with a thirty-day letter, which gives them thirty days to respond to the changes.

For example, if a taxpayer claimed a deduction for a business expense that was not actually related to their business, the revenue agent's report would show that the deduction was disallowed and the taxpayer would owe more taxes.

Another example would be if a taxpayer failed to report all of their income on their tax return. The revenue agent's report would show the additional income and the resulting increase in taxes owed.

The purpose of the revenue agent's report is to inform the taxpayer of any adjustments made to their tax return and give them an opportunity to respond before the changes become final.