The MAS program accepts applications for admission only once a year. The deadline is February 15. Successful applicants from non-UIUC accounting program can only start in the Summer II term (Summer II classes start in June). Applications can be processed on-line through the Graduate College.
usually, such program is one-year and starts in May or June. In US there are many of such 'early' programs. You may get a firm answer when you write to the school. I am not sure about that.