Please note, this form is optional, and you do not need to fill it out. If you already have this form, you may continue to fill out the form, but you are not required to fill it out. The tax is assessed to you the same whether you fill out Form W9 and pay federal income taxes. Form W9, Request for Taxpayer Identification Number (TIN) and Certification. ▷ Go to for instructions and the latest information. Give Form to the. About Form W-9, Request For Taxpayer Identification — IRS. Fill the form exactly as shown at the bottom of this article. The Form W9 should be accompanied by a copy of the original tax return (if you have not already sent it to the IRS). Note: The name and identification number or certification number for the person who answered the Form W9 has not affected your tax obligation. You need this form to pay your federal income tax. You cannot file and file a paper return to claim the federal income tax exemption for California if you have filed Form W-9. Furthermore, you cannot deduct your ordinary and necessary expenses for lodging or transportation in California for the tax year or any prior tax year, even if such expenses also appear on your Form 1040, Form 1040A, or Form 1040EZ. This is not a tax form. It is meant to help you if you have questions. It also helps to send some tax withheld through the mail if you need to. You may not owe the money you owe if you have filled out the appropriate forms and have sent them to the proper address. Fallout and print the form on page one, then follow the instructions on pages two through six. The IRS will send you copies of the Form W9. It will also send you additional information after you pay the tax. You should wait until you have received all the instructions before you take any additional steps based on these instructions. For example, if you are filing a return on a later date, you may want to mail in and prepare the form. The information on this form is also known as the “form that you send.” After you submit Form W-9, you can also go to Form W99-A, Self-Employment Tax Return. Important: For the avoidance of doubt, the IRS encourages taxpayers to be familiar with their tax situation in California.