We highly recommend that you go to the SSN website for the most up to date information.
Social Security Number (SSN)
How to obtain
Once you have received your Employment Authorization Document Card, you may then apply for your Social Security # (SSN). This number is similar to the Canadian Social Insurance # - it is what employers use to report your taxes to the U.S. Internal Revenue Service. It is free to apply.
When you are applying for your SSN, ask the customer service rep for the telephone number to call after 24 hours to find out the SSN that has been assigned to you. You will not get the card right away, but they can give you the number over the phone. You are able to apply for a job without having received the card. You will have to provide proof that you have applied to your potential employer; however, some employers may not be willing to hire you until you have received your actual card.
One side benefit to obtaining your social security number while in the U.S., is that it will allow you to apply for U.S. Credit. Your CF Member is also eligible to apply for an SSN with just his or her green passport/visa and I-94 documentation – no EAD required.