If "it" that says a check was mailed is "Where's My Refund?" on the IRS web site, there is no other way to confirm that. You just have to wait until you get the check. I suspect that when "Where's My Refund?" says a check was mailed, it really means that they printed the check. It wasn't necessarily put in an envelope or given to the Postal Service on that date. And the mail is often slow. So give it some more time. It could take as much as two weeks from the date they say they mailed it until you receive it.