Check out the IRS "Do You Need a New Name Change?" website to see if you are eligible to transfer your EIN.
Write a letter (on company letterhead if possible) informing the IRS of the name change. Include the business name (both old and new), the EIN, and your mailing address.
Sign the letter. If you are a sole proprietorship, the business owner should sign. For a corporation, a corporate officer should sign. For a partnership, one of the partners should sign the letter.
Mail the letter to the IRS at the address you you sent your tax return to last year.