When you start a new job, you fill out a W-4 form to provide your employer with information needed to accurately calculate how much federal income tax to withhold from your paycheck. This includes details such as your tax filing status, other jobs or spouse's income, dependents, and any additional income or deductions you expect, helping your employer withhold the correct amount of tax throughout the year to avoid owing a big tax bill or giving an interest- free loan via a refund.
