Make sure to select the column letter (at the very top) to highlight the entire section, in which you want to apply this special formatting.;
, Select "Format Cells..."

, Several different types of special information fields will appear in the middle, from which you can select.
 The highlighted column will now format SSNs properly, which includes adding dashes between the digits and not omitting any numbers.
Click on the column in which you are entering one or more SSNs.
Right-click and review the dropdown menu that appears.
In the Format Cells menu box, select the Special category from the left sidebar.
Click on Social Security Number, then press OK.
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