Do I need to mail anything to the school after I have submitted my application online?
Most schools require certain supplemental forms to be printed out and mailed in (such forms include teacher recommendation letters and transcript request forms). You will submit your application online, and then mail in these Supplemental Forms. If the school you are applying to requires Supplemental Forms, you will find them within the application--simply print them out from the Apply Online system. If you are unsure which forms are required, read the application instructions. Your application will not be considered complete until all parts of the application have been submitted to the appropriate Admissions Office.
-- Terry Hofmann, Associate Dean and Director of Graduate Programs, College of Business Administration, Northeastern University

Due to the confidential nature of certain aspects of the application, many schools do require that certain supplemental forms to be printed out and mailed with official authorization (such forms include personal, academic or professional recommendation letters and official transcript request forms). You may submit your application online, and then mail in these supplemental forms. If the school you are applying to requires supplemental forms, you will find them within the paper copy of the application or simply print them from the online application system. The application instructions should clearly indicate which forms are required.
-- Robert Taggart, Associate Dean, Graduate Programs, Boston College Carroll School of Management