For the first time ever, the other day, I saw an its with an apostrophe AFTER the s!! That error sent me over the edge. This grammar Nazi decided the day of reckoning had arrived.
Most of the time, when I see an its error in print somewhere, I close my eyes, and breathe deeply. For a minute or so. Sometimes, though, if the offending document allows, I snatch my pen from my purse, steal a furtive glance to see if anyone is watching, and then scribble in the correction. Other times, when the error appears on a website, I send polite and specific emails using the "Contact Us" feature. The website managers are very generous in their appreciation (no irony here at all; they are always gracious and thankful), and make the correction. I even offer to provide proof-reading services, given that theirs need shoaring up. No takers yet, though. Odd, really, considering the number of errors I spy.
So, for the record, it’s very easy to know when to use it’s or its. If you can substitute it is for it’s, as in the preceding sentence (it is very easy to know when to use . . .), use it’s. Use its in ALL other situations. ALL other situations. NEVER, of course, add an apostrophe after the s.
Some people might ask, why doesn’t its need an apostrophe when it shows possession? Don’t we use apostrophes to show possession? Yes, in the case of nouns. Its, however, and its relatives yours, ours, theirs, and hers, are possessive adjectives. Their very nature is to show possession. It’s included, like the tip in the restaurant bill or the food and beverages in an all-inculsive resort. You could even call it built-in, just like the water dispenser in a fridge, or the microphone in the latest iteration of iPhone ear buds. One neat, efficient package. No apostrophes needed.
Voilà the truth about when to use its or it’s. Quite simple, really. No need for errors. Ever.