The federal I-9 and W-4 forms are used by employers to verify the employment eligibility and tax withholding information of their employees.
The I-9 form is used to verify the identity and employment authorization of employees, while the W-4 form is used to determine how much federal income tax should be withheld from an employee's paycheck. Both forms are required by federal law, and employers who fail to complete them correctly can be subject to fines and penalties.