Introduction The federal income tax is a pay-as-you-go tax. This means you must pay the tax as you earn or receive income during the year. As a wage earner, you pay federal income tax by having it withheld from your pay during the year. This is your "withholding." Your withholding is based on the number of allowances you claim when you file Form W-4, Employee's Withholding Allowance Certificate, with your employer. Comments and suggestions. We welcome your comments about this publication and your suggestions for future editions. You can e-mail us while visiting our web site at www.irs.gov. You can write to us at the following address: Internal Revenue Service Technical Publications Branch W:CAR:MP:FP:P 1111 Constitution Ave. NW Washington, DC 20224 We respond to many letters by telephone. Therefore, it would be helpful if you would include your daytime phone number, including the area code, in your correspondence.