When must an IRS employee secure written supervisory approval for a penalty assessment to be valid?

This case presents a conflict regarding an important question of statutory construction under the Internal Revenue Code. The Code provides that no penalty shall be assessed unless the initial determination of such assessment is personally approved in writing by an immediate supervisor. Courts of Appeals have diverged on when an IRS employee must secure supervisory approval for a penalty assessment to be valid. The question presented is: When must an IRS employee secure written supervisory approval for a penalty assessment to be valid?