Exceljet

Quick, clean, and to the point

Apply or remove underscoring

Windows shortcut 
CtrlU
Mac shortcut 
U

This shortcut toggles underlining on and off for the current selection.

On Windows, Ctrl 4 also toggles underlining.

Related videos

The videos below show how this shortcut can be used.
In this video, we'll look at the shortcuts you can use for find and replace in Excel.
In this lesson, we cover shortcuts you can use to format cells and other objects.