Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Under what circumstance will the IRS charge you a late-payment penalty for taxes?
In practice the IRS seems to apply the late payment penalty when they issue a written paper notice.  Those notices typically have a pay-by date where no additional penalty applies.  The IRS will often waive penalties, but not interest or tax due, if the taxpayer presses the issue.