What do the B mean in a IRS cp 575 B letter?

The "B" in the IRS CP 575 B letter indicates that the letter is a notification related to a business entity's Employer Identification Number (EIN). Specifically, it typically informs the recipient that the IRS has processed their application for an EIN and provides important details about their tax responsibilities. Recipients should keep this letter for their records, as it serves as official documentation of their EIN.