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 have already filed your tax return for your business, then you can also notify the IRS of a name change via mail. In order to change your LLC name with the IRS, you'll need to mail them a letter and show proof of the state approving your LLC name change. In addition, you must furnish a new. Form W-9 if the name or TIN changes for the account; for example, if the grantor of a grantor trust dies. Penalties. You can find the CP or LTR number on the right corner of the letter.