Form W-4 is filled out by employees when they start a new job to tell their employer how much federal income tax to withhold from their paychecks. It affects the amount of tax deducted throughout the year but is not a tax return form. The information on your W-4 — such as number of dependents, additional income, and other deductions — determines how accurately your employer withholds taxes. An incorrect W-4 could result in owing taxes or getting a large refund at year’s end. However, to actually file your taxes, you must complete Form 1040. Mistaking W-4 for a filing form is a common error, especially for those new to the workforce. While W-4 helps manage your withholdings during the year, it does not replace the need to file an annual return using the correct form.