This document contains final regulations providing guidance under section 3402(f) of the Internal Revenue Code (Code) for employers and employees relating to the Form W-4, "Employee's Withholding Allowance Certificate." The regulations provide rules for income tax withholding when the IRS notifies the employer and the employee of the maximum number of withholding exemptions permitted. The regulations also provide rules for the use of substitute forms and preserve the IRS's ability to require the submission of certain copies of withholding exemption certificates. The regulations primarily affect taxpayers who are employers and employees.