So... people have asked in the Payment Agreement thread as well as many other forum threads about how to pay online and the other payment methods OTHER than cheque.
Well... the SAC website was linking to the incorrect file so I wasn't able to find the proper PDF file. However, Theresa from the Student Accounts & Cashiers Office kindly provided me with the correct link that we've been looking for:
Here it is:
http://www.mcmaster.ca/bms/student/p..._methods.p df
That PDF explains everything you need to know about the online payment method and the various other options you have!