How long does it take for the IRS to notify me on the status of my personal tax extension (IRS Form 4868)??

The short answer is that depends on volume and how quickly the IRS computer are processing. As a rule, you will generally hear back within an hour or so. Keep in mind that as long as you submit your tax extension on time, even if it’s rejected by the IRS for whatever reason, your extension is still considered timely provided you fix the error and resubmit within 5 days of the deadline.