Excel provides both single and double underlining. It also provides a special variant of each for numbers using the Accounting format.
Let's take a look.
For most basic underlining, you can just use the Underline button on the ribbon. The Underline button toggles underlining on and off. It also provides a menu for selecting single and double-underlining.
The Underline button remembers your last selection. For example, if you apply a Double Underline, the button will keep that selection until you select Single Underline again.
Excel actually provides two more underline options for use with the Accounting number format. You can't see these options on the ribbon, but in the Format Cells dialog box, you'll find them listed in the Underline menu as "Single Accounting" and "Double Accounting."
The accounting variants of underline options increase the row height a bit and provide more space between the underline and the text. We can see this if we apply the different formats side by side.
Note that Excel will automatically apply the accounting version of underlining in cases where the selection contains only cells using the Accounting format. There's no indication that this has been done, but you can see the accounting version has been applied in the Format Cells dialog box.
This doesn't happen with other number formats or when the selection contains content in different formats. For example, if we apply Underlining to cells in the Currency format, Excel does not use the accounting version. In fact, when the selection contains any format but Accounting, normal underlining will be applied.
Finally, depending on your needs, keep in mind that applying a border on the bottom of cells is another way of underlining content in Excel. Unlike text underlining, cell borders run edge to edge across the entire cell.
We'll look at borders more closely in an upcoming lesson.