SS4 is the IRS form required to obtain an EIN Number (Employer Identification Number, often called Tax ID Number). The EIN Number/Tax ID number can be considered a Social Security number for your business. This usually requires opening a bank account in the name of the business and appropriate payments and accounts for any salary/payroll employees in your company.

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  Do You Need a Federal EIN for Your Business Entity?

  In general, unless your business is a sole proprietorship with employees and there is no separate legal entity for your business, you need to obtain an EIN Number.

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  What is an Employer Identification Number (EIN)?

  Also known as a "tax ID number," an EIN Number is a business federal tax ID that acts like the Social Security number for your business. Your EIN Number helps you file tax returns for your business, usually requiring you to open a business bank account under your business name, properly pay and account for salaries and payroll for your company's employees. Helps in, and otherwise establish credit for, your business. and as a legal business entity

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  Partnerships: an EIN is required for all general partnerships and limited partnerships.

  Multiple-member LLCs: This type of business entity needs an EIN regardless of whether you have employees.