Form SS-4

Form SS-4 (Application for Employer Identification Number) is an IRS form used to apply for an Employer Identification Number (EIN), a unique nine-digit tax identification number assigned to businesses, estates, trusts, and other entities. Often referred to as a Federal Tax Identification Number or FEIN, an EIN functions like a Social Security Number for business entities and is essential for tax reporting and business operations.

You need to file Form SS-4 when starting a new business, hiring employees, opening a business bank account, establishing a corporation or partnership, operating as a trust or estate, withholding taxes on non-wage income, or filing employment, excise, alcohol, tobacco, or firearms tax returns. Sole proprietors without employees may use their SSN for tax purposes but often obtain an EIN for privacy protection and professional credibility.

Form SS-4 requires information about the entity type (sole proprietorship, partnership, corporation, LLC, estate, trust, etc.), the responsible party’s name and taxpayer identification number, business name and address, reason for applying, principal business activity, and the date business started or was acquired. The responsible party must be an individual with control over the entity’s funds and assets, not a nominee or representative.

The fastest way to obtain an EIN is through the IRS online application, which provides an EIN immediately upon completion during business hours. Alternatively, you can submit Form SS-4 by fax and typically receive your EIN within four business days, or by mail with processing taking approximately four weeks. International applicants without U.S. Social Security Numbers must call the IRS international line to obtain an EIN.

Once assigned, an EIN is permanent and remains with the entity even if the business closes, unless the entity structure fundamentally changes or dissolves completely. You cannot cancel or relinquish an EIN, and the same EIN cannot be transferred to another business entity. If your business undergoes significant structural changes, such as incorporating a sole proprietorship or changing from a partnership to a corporation, you may need to apply for a new EIN.