Some IRS notices are sent via certified mail, such as the Notice of Intent to Levy. I suggest getting your IRS letter and taking action immediately. The IRS will give you time to deal with the matter, but make sure you respond to all required actions in a timely manner. Click the article below to read more information on IRS notices.
https://turbotax.intuit.com/tax-tips/irs-letters-and-notices/dont-fear-the-tax-man-handling-irs-lett...