You must complete Form W-4 so that the Payroll Division can calculate the correct amount of tax to withhold from your pay. Federal income tax is withheld from your wages based on marital status and the number of allowances claimed on this form. You may also specify that an additional dollar amount be withheld. You can file a new Form W-4 anytime your tax situation changes and you choose to have more, or less, tax withheld.
Whether you are entitled to claim a certain number of allowances or exemption from withholding is subject to review by the IRS. Your employer may be required to send a copy of Form W-4 to the IRS.