Insure, Ensure, Assure: Being Sure

Josh sent this note from his lender. It's hard to see, but they're asking him to "please check the payoff date to insure it is correct."

What they want to do here is ensure it's correct. "Insure" with an i is best used when you're talking about, say, an insurance policy. (And that's an easy way to remember it.) "Ensure" with an e is best used when you're making sure of something. To "assure" someone of something is to pledge, promise, or declare earnestly that something is the case. (And you're an "ass" if your assurance doesn't pan out.)