By default, Excel doesn’t show the leading zero in any non-decimal numerical data set. But if you need to show the leading zero — usually because of some weird numbering system at your job, it’s easy to keep that zero in its place.
In any individual Excel document, select one of more cells (or a whole column or row), and then Ctrl+1 to open the “Format Cells” menu. (MacOS users, use the Command+1 instead.)
