An employment authorization card or document ("EAD") allows an alien to work for any employer at any time during the validity period of the card.  Several nonimmigrant visa categories including E-1, E-2, E-3, H-1B, H-2, L-1, and TN-1 allow work without an employment authorization card for only a specific employer.  Aliens with EADs may only work during the validity period of the card.  This means that if you wait too long to renew your card, you must stop working when your card expires while you are waiting for the replacement to arrive.

Those eligible to file an I-765 application for employment authorization include:

1. Applicants with a pending adjustment of status application
2. Students and an endorsed I-20 allowing optional practical training
3. Spouses of E-1 treaty traders and E-2 treaty investors
4. Spouses of L-1 multinational transferees
5. Applicants for cancellation of removal in the immigration court
6. Applicants for asylum (starting 180 days after the application)
7. Certain beneficiaries of Temporary Protected Status (TPS)

There are many other types of applicants eligible to file for work authorization, but listing them here would make this page confusing for most readers.

An employment authorization card is designated Form I-766 and as of 2010, the card looks like this:

Also starting in 2010, the EAD is preprinted with advance parole authorization, which you can see below written on the card "VALID FOR REENTRY TO U.S."

The earliest you may file to renew your EAD using form I-765 is 120 days before your current card expires.  USCIS does not use the mailbox rule, so they count the days from the time they receive the application.  If you send your application by overnight express mail, the earliest you can file is 121 days before your current EAD will expire allowing one day for delivery.

If your EAD is lost or stolen,  you must apply to replace it using form I-765 and not form I-824.  There is a place on the form to indicate that your EAD was lost or stolen.

An EAD does not confer lawful status and is merely permission to work incident to whatever status you have.  If you have an EAD because you have an application to adjust status pending, if your application to adjust status is denied, but your EAD has remaining validity, this does not allow you to remain in the United States.  Similarly, if you are the spouse of an E-2 treaty investor and you possess an EAD valid for two years, if your treaty investor spouse loses his or her status, you lose yours and your EAD does not allow you to remain in the United States.