It is possible to fill out the FAFSA without a FSA ID. In fact, it may be necessary in cases where one or both parents doesn’t have a Social Security number and therefore, can’t create a FSA ID. In this event, you can still fill out the FAFSA form online, but you’ll need to print it out, sign it by hand and submit the application via mail.In the event that all parties have a Social Security number, having a FSA ID provides you with the safest and fastest way to complete and submit the FAFSA form.