Use 5–12% extra space with caps, but not with lowercase
Letterspacing (also known as character spacing or tracking) is the adjustment of the horizontal white space between the letters in a block of text. Unlike kerning, which affects only designated pairs of letters, letterspacing affects every pair.
Lowercase letters don’t ordinarily need letterspacing.
Capital letters usually appear at the beginning of a word or sentence, so they’re designed to fit correctly next to lowercase letters. But when you use capital letters together, that spacing is too tight. That’s why you should add 5–12% extra letterspacing to text in all caps or small caps. This is particularly important at small sizes (e.g., the footer of a court filing).