Two options for spelling the word or words that sound like /ITS/:
Simplest way to tell the
Why do people automatically (but incorrectly) add an apostrophe to the possessive pronoun its?
Possessive forms like “the boat’s rudder” or “Janice’s project” use apostrophes—why not its?
So /ITS/ will never be spelled “it’s” unless it is a contraction for “it is” . . . . If you remember that, you can avoid the error.)
How I learned this rule as a kid in the mid-20th century . . .