Learn how to change your business name with the IRS. Sole Proprietorship.Write to us at the address where you filed your return, informing the Internal Revenue Service (IRS) 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. Are you planning an IRS business name change? You may not need a new EIN. The Certificate of Assumed Name must be typed or printed in black ink. All printing and signatures must be of sufficient clarity and darkness.