Purpose of This Publication The purpose of this publication is to help you check your withholding and, if necessary, prepare Form W-4 to adjust your withholding. When you first begin a job, you must complete a Form W-4 and give it to your employer to establish your initial withholding. You can adjust your withholding by filing a new Form W-4 with your employer at any time. Note: You do not have to file Form W-4 each year unless you need to adjust your withholding.