Which document must be obtained from new employees?

The requirement to obtain a document from new employees in the context of payroll and tax purposes is primarily fulfilled by the I-9 form, which is designed to verify an employee's identity and authorization to work in the United States. Thus, the I-9 is the correct answer.

The focus of the I-9 is to ensure compliance with the Immigration Reform and Control Act. Employers must collect this form from new hires and review the appropriate identification documents to establish that the individual is legally allowed to work in the country.

While the Social Security card is important for confirming Social Security numbers and can be used as one of the documents for the I-9 process, it is not a standalone requirement for employment. The W-4 is necessary for tax withholding purposes and must be filled out, but it does not verify identity or employment eligibility. The W-2, on the other hand, is a year-end tax form that summarizes an employee's annual earnings and withheld taxes but is not required from new hires at the start of their employment.