Make sure to keep calling them so that your check is not lost or put in the wrong application. Wait for your application to be sent out and once the school receives it, call them and verify that they have your check (and ofcourse check your bank to see if it goes through). If you have not already done so, do not send secondary checks till the school receives your application. I know that it says at the time of submission, but it takes 3-4 weeks for schools to get your file and we want to avoid confusions and lost checks that will postpone review of your application. Let me know if you have further questions.