The current Form I-9 is five pages. The first three pages contain instructions for completion of the form. Page three contains one paragraph about the paperwork reduction act. Page four is the form, and page five is the list of acceptable documents. The irony is that the government could reduce paper work by getting rid of the third page of instructions. The reality is that the instructions should probably be about ten pages since almost no one does the I-9 right and most companies would be surprised to find out they have liability sitting in their HR files due to this one page form.

Page five is not a list of forms of identification, it is a list of documents you may provide to prove you have the legal right to work within the United States. It just happens to be that some forms of identification also prove work authorization for some citizenship statuses. For example, if you are a U.S. citizen your drivers license and social security card or your passport prove this. Edit: The I-9 form however does establish identity in addition to right to work because of the overlap.

Fun tip: Lots of companies request specific documents for the purpose of completing this form (drivers license and ssn usually), this is a form of discrimination and you have a legal right to complain to the Office of Special Council www.osc.gov

Disclaimer: I am employed by a company that specializes in supporting companies processes for this specific document.