IRS Form SS-4: Application for Employer Identification Number (EIN) (2026)

Who needs an EIN

Form SS-4 is the application for an Employer Identification Number (EIN) — the federal tax ID that identifies a business, estate, or trust the way an SSN identifies a person. You generally need one if you: - Hire employees, - Operate as a corporation or partnership, - File certain excise or employment tax returns, or - Administer an estate or trust.

Many single-member LLCs and sole proprietors get one too, to open a business bank account and keep business and personal finances separate.

What you'll provide

• The entity's legal name and structure,
• The responsible party (the person who controls the entity) and their taxpayer ID,
• Your reason for applying (new business, hiring, banking), and
• The expected number of employees and your accounting year.

Common mistakes to avoid

• Naming the wrong responsible party. It must be a real person who controls the entity, not another company.
• Applying for more than one EIN for the same entity — you only need one, and it's permanent.
• Mismatched entity name and structure, which slows processing.

After you apply

An EIN is issued for the life of the entity — it's never reused or reassigned, even after a business closes. Store the confirmation somewhere safe; you'll need the number to open bank accounts, run payroll, and file returns.