A W-4 form is an IRS document that employees complete for their employer to determine how much should be withheld from their paycheck for federal income taxes and sent to the IRS. Accurately completing the W-4 form will help employees avoid overpaying their taxes throughout the year or owing a large balance at tax time. The form tells the employer how much to withhold from the employees wages for federal income tax. The W-4 form includes information such as the employees filing status, multiple jobs adjustments, amount of credits, amount of other income, amount of deductions, and any additional information that may affect the amount of tax withheld. Employees fill out a new W-4 form if they start a new job or change the amount withheld from their pay. They may also need to submit a revised W-4 if their situation changes, such as getting married or divorced, having a child, or picking up a second job. The purpose of the W-4 form is to ensure that the correct amount of federal income tax is withheld from an employees paycheck throughout the year.