SS4 refers to the "Social Security Administration Form 4," which is used for various purposes related to Social Security benefits. This form is typically utilized to apply for a Social Security Number (SSN) or to request changes to an existing SSN. It is essential for individuals seeking employment, government benefits, or other services that require identification. The SS4 form is crucial for businesses as well, particularly when applying for an Employer Identification Number (EIN). An EIN is necessary for tax purposes and is often required when hiring employees or opening a business bank account. Proper completion of the SS4 form ensures compliance with IRS regulations.