when do you fill out a w4

A W-4 form should be filled out when starting a new job to inform the employer of the correct federal income tax withholding amount. It is important to complete it as soon as employment begins, ideally by the first day or shortly thereafter. Additionally, the W-4 should be updated anytime there are major life changes such as marriage, divorce, having a new baby, or changes in dependent status to ensure accurate tax withholding. Employees are also encouraged to review their withholding at least annually or when their financial situation changes to avoid under- or over-withholding.