There are two types of challenges here first being inserting a minus sign in excel(or hyphen in string) and the other is inserting a negative number in a cell in excel.
If you start typing minus symbol at the beginning, excel will treat it as formula and thrown an error.
Let’s see how we could insert a minus sign “-” before a value in excel.
There are two aspects to it, one is if you have alphanumeric values in a column and you would like to insert a minus sign before the value so the resultant value is text string only.
Enter the formula below, we will just concatenate a minus sign at the beginning of the value as show below.
In the other scenario when your data is completely numeric and you want to have a minus sign before each value, just multiply them with -1 as show below.
The formula will be =-1*A2
Hope this helped.