Which identification number is used by the IRS for tax identification purposes?

The Employer Identification Number (EIN) is the correct identification number used by the IRS for tax identification purposes. The EIN serves as a unique identifier for businesses and is required for various tax-related activities, such as filing tax returns, opening bank accounts, and reporting employee wages. This number is typically used by employers, partnerships, corporations, and estates, among others.

Other options, while related to identification in specific contexts, do not serve the same purpose as the EIN for tax matters. For instance, a State License Number is specific to the licensing of professionals within a particular state and is not recognized by the IRS for tax identification. The Provider Identification Number (PIN) and Unique Provider Identification Number (UPIN) are used within healthcare and provider systems for billing and identification purposes but are not utilized by the IRS for tax identification. Thus, the EIN is essential for businesses in their dealings with the IRS.