Sole Proprietorship. Write to us at the address where you filed your return, informing the Internal Revenue Service (IRS) of the name change.Learn how to change your business name with the IRS. 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. If you've changed your legal or business name, you might need to notify the IRS or the Social Security Administration (SSA). Are you planning an IRS business name change? You may not need a new EIN. Just file your tax return using your new name and it will be matched up to the Social Security database. You don't have to mail a special letter to the IRS to change your LLC name.