 A new or returning employee must have a valid I-9 Form completed within. the 3 days of employment.  All original documents must be provided for verification within 3 business. days of employment.  In conjunction with the I-9, all non-citizens must also provide an I-20 Form, a DS-2019 Form, or an I-797 Form for employment authorization.  Social Security Cards with “Valid for Work Only with INS Authorization”.
http://www.uta.edu/hr/records-services/documents/I-9%20Guide.pdf
EAD is the document (Form I-688, Form I-688A, Form I-688B, Form I-766, or any other successor document issued by USCIS) that proves as evidence that the holder is authorized to work in the United States. Sample EAD.
http://www.immihelp.com/immigration/employment-authorization-document.html
Not required to apply for an EAD until 90 days before the expiration of current EAD. (c)(8) - Asylum Applicant (with a pending asylum application) Asylum Applicant (with a pending asylum application) who Filed for Asylum on or after Jan 4, 1995.
http://www.immihelp.com/immigration/employment-authorization-document.html
The combined travel and employment authorization card will be valid for one year, if the applicant’s immigrant visa is currently available. visa is not currently available, then the combined card will be valid for two years.
https://www.uscis.gov/sites/default/files/USCIS/About%20Us/Electronic%20Reading%20Room/Customer%20Service%20Reference%20Guide/Employment_Authorization.pdf
a person’s wages to the government. and to determine a person’s eligibility for. Social Security benefits. You need a Social. Security number to get a job, collect Social. Security benefits, and receive some other. government services. If you’re temporarily in the United States to.
http://www.ssa.gov/pubs/EN-05-10107.pdf
keep the I-9 records for at least three years past the date of hire, or one year after the employees leaves the job, whichever is later (however, it's a good idea to keep all employment records at least seven years after the employee leaves employment).
http://www.twc.state.tx.us/news/efte/i_9_requirements_lists.html
How long the work permit lasts depends on your current immigration status, or what type of visa you are here on. Most EADs are valid for one year. Obviously, however, no person will be given a work permit that lasts longer than their permitted stay in the United States.
http://www.alllaw.com/articles/nolo/us-immigration/how-long-does-work-permit-ead-last.html
The combined travel and employment authorization card will be valid for one year, if the applicant’s immigrant visa is currently available. If the immigrant. visa is not currently available, then the combined card will be valid for two years.
https://www.uscis.gov/sites/default/files/USCIS/About%20Us/Electronic%20Reading%20Room/Customer%20Service%20Reference%20Guide/Employment_Authorization.pdf
I-9 REQUIREMENTS - DOCUMENT LISTS. Ever since passage of the Immigration Reform and Control Act in 1986, employers have had to verify the employment authorization of each employee they hire. This is done with the I-9 form, a copy of which must be completed for each newly-hired employee.
http://www.twc.state.tx.us/news/efte/i_9_requirements_lists.html
You may receive this card when you file Form I-765, Application for Employment Authorization, and Form I-131, Application for Travel Document, concurrently with or after filing Form I-485, Application to Register Permanent Residence or Adjust Status. You must file the Form I-765 and I-131 at the.
https://www.uscis.gov/sites/default/files/USCIS/About%20Us/Electronic%20Reading%20Room/Customer%20Service%20Reference%20Guide/Employment_Authorization.pdf
how long  are employment authorization document good for
An employment authorization document is good for one year.