Paychecks will come on the same day pretty consistently. Over the years, it's happened to me maybe 3-4 times that I've received them 1-2 days in advance or late. It can happen and it shouldn't be an issue. Wait until Friday (the real day you should have received the paycheck) to see if that's the case. If you don't receive anything on Friday, then it was the real paycheck, just two days in advance. If you receive another paycheck on Friday, then call HR or the bank to inform them about a possible error. It's illegal I believe to spend money that is not yours, even if it's in your account (because of a human or software error from the bank/employer)