When must employees provide their completed Form W-4 to the contractor?

Employees are required to provide their completed Form W-4 to the contractor when they start work. This form is essential for establishing the employee's tax withholding preferences and ensures that the correct amount of federal income tax is withheld from their pay. Completing this form at the start of employment allows for accurate payroll processing, helping to avoid any tax issues that might arise from improper withholding. By providing this information promptly, employees enable their employers to fulfill their tax obligations right from the outset of employment, which is critical for both parties involved.