Final answer:
An employee might not be on the company's payroll because the company requires all employees to sign the necessary state and federal tax forms before they can be added, as stated in one of the sentences.
Step-by-step explanation:
The sentence that specifically states why an employee might not be on the company's payroll is: The company will decline to put any employee on payroll who has not signed the required state and federal tax forms. This statement makes it clear that compliance with tax form requirements is a precondition for being placed on payroll. In the context of the United States, it is standard for employers to require employees to complete forms like the W-4 to ensure proper withholding of payroll taxes, which include both deductions from an employee's wages and taxes paid by the employer.