If you are filing a current year Form 1065, mark the appropriate name change box on the form: Page 1, Line G, Box 3. The namechange letter should clearly state that your business name has changed.The first step is to file a form called the Certificate of Amendment with the Secretary of State and wait for it to be approved. The letter to the IRS will vary depending on your type of business and should include your company's tax ID, address, and an explanation of the name change. How do I fill this out? To fill out this form, you need to provide the old and new company names, your federal identification number, and contact details. Write a letter requesting a name change to the IRS. The letter must clearly state your old name and the new name. Simply check off "name change" at the top of Form 1065 when taxes are filed. You will also have to submit new W9 forms any time you change your name, business name, address or tax ID number.