Final answer:
The document used by employers to establish work authorization in the U.S. is the Social Security Card.
Step-by-step explanation:
The document used by employers to establish who is authorized to work in the U.S. is the Social Security Card.
Employers are required to ask for proof of citizenship, and the Social Security Card is one of the acceptable documents in establishing identity and work authorization.
For example, when completing Form I-9, which is used to verify the identity and employment eligibility of individuals hired for employment in the United States, employees can present their Social Security Card.