SS-4 EIN Application Guide - From SS-4 Form Completion to EIN Letter

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SS-4 EIN Application Guide – Are you starting a new business, hiring employees, or setting up a trust? Obtaining an Employer Identification Number (EIN) is often one of the first essential steps for tax compliance and business operations in the United States. The IRS Form SS-4, officially known as the Application for Employer Identification Number, is the key document used to request this unique nine-digit identifier. In this comprehensive guide, we’ll walk you through everything from understanding who needs an EIN to completing the SS-4 form step by step, submitting your application, and receiving your EIN confirmation letter. Whether you’re a sole proprietor, corporation, or nonprofit, this SEO-optimized article draws from official IRS resources to ensure you’re equipped with accurate, up-to-date information as of 2026.

What Is an EIN and Why Do You Need Form SS-4?

An Employer Identification Number (EIN), also called a Federal Tax Identification Number, is a nine-digit code (e.g., 12-3456789) assigned by the Internal Revenue Service (IRS) to identify businesses and other entities for tax purposes. It’s similar to a Social Security Number (SSN) but for your business entity. The EIN is used for filing tax returns, opening business bank accounts, applying for licenses, and handling payroll.

Form SS-4 is the official IRS application form for obtaining an EIN. It’s required for most entities that engage in business activities, but you can also apply online without physically filling out the paper form. The latest revision of Form SS-4 is from December 2025, which includes updates like new fax and mailing addresses, emphasis on online applications, and restrictions on telephone applications for domestic users.

Who Needs an EIN?

Not every individual or entity requires an EIN, but it’s mandatory in many cases. According to IRS guidelines, you need an EIN if:

You operate as a corporation, partnership, or multi-member LLC.
You have employees or plan to hire them.
You file employment, excise, or alcohol/tobacco/firearms tax returns.
You withhold taxes on income paid to non-resident aliens.
You’re involved with trusts (except certain grantor-owned revocable trusts), estates, nonprofits, farmers’ cooperatives, or plan administrators.
You’re a sole proprietor with employees, a Keogh plan, or filing certain tax returns like Schedule C with qualified plans.

Even if not required, sole proprietors often get an EIN for privacy (to avoid using their SSN on business documents) and to separate personal and business finances. Government entities, Indian tribal enterprises, and household employers may also need one. If you’re unsure, check the “Do I Need an EIN?” section in the Form SS-4 instructions.

Step-by-Step Guide to Completing Form SS-4

If you’re applying by fax or mail, you’ll need to fill out the physical Form SS-4. For online applications, the IRS uses an interview-style process that mirrors the form’s questions. Gather your information beforehand: legal business name, addresses, responsible party’s details, entity type, and more. Use “N/A” for non-applicable fields. Here’s a line-by-line breakdown:

Lines 1-3: Entity Name and Contact

Line 1: Enter the legal name of the entity or individual (e.g., full name for sole proprietors, trust name for trusts).
Line 2: Add any trade name or DBA if different from Line 1.
Line 3: Provide the name of an executor, administrator, trustee, or “care of” contact.

Lines 4-6: Addresses and Location

Lines 4a-4b: Mailing address (include room/suite, city, state, ZIP; full country for foreign addresses).
Lines 5a-5b: Physical street address if different (no P.O. boxes).
Line 6: County and state of principal business location.

Lines 7-9: Responsible Party and Entity Type

Lines 7a-7b: Name and TIN (SSN, ITIN, or EIN) of the responsible party (e.g., owner, principal officer, or trustee). This must be an individual, not a business.
Lines 8a-8c: For LLCs only—indicate yes/no, number of members, and if organized in the U.S.
Line 9a: Check the entity type (e.g., sole proprietor, corporation, nonprofit). Specify details like form number for corporations.
Line 9b: For corporations, state or foreign country of incorporation.

Lines 10-12: Reason and Dates

Line 10: Reason for applying (e.g., started new business, hired employees; specify type).
Line 11: Date business started or acquired (month/day/year).
Line 12: Closing month of accounting year (e.g., December for calendar year).

Lines 13-15: Employees and Wages

Line 13: Highest number of employees expected in the next 12 months (agricultural, household, other; enter 0 if none).
Line 14: Check if you want to file Form 944 annually (for low employment tax liability ≤$1,000).
Line 15: First date wages or annuities were paid (or N/A).

Lines 16-18: Business Activity and Prior EIN

Line 16: Principal activity (e.g., retail, manufacturing).
Line 17: Specific description of products/services (e.g., “residential construction”).
Line 18: Indicate if you’ve previously applied for an EIN (yes/no; provide prior EIN if yes).

Third-Party Designee and Signature

Optionally authorize a designee (e.g., accountant) to receive your EIN and handle questions.
Sign and date the form (must be an authorized person like the owner or officer).

Common mistakes to avoid: Using abbreviations, leaving required fields blank, or applying multiple times. Always match names to legal documents.

How to Submit Your SS-4 EIN Application?

The IRS offers multiple free methods to apply, but use only one to avoid duplicate EINs. Online is recommended for speed.

Online Application

Eligibility: Principal business in the U.S. or territories; responsible party has a valid TIN.
Steps: Visit IRS.gov/EIN, answer questions in one session (expires after 15 minutes of inactivity), submit, and receive your EIN immediately.
Availability: Monday-Friday 6 a.m.-1 a.m. ET (next day), with weekend hours.
Benefits: Free, instant, and printable confirmation.

Other Methods

Phone: Only for international applicants (no U.S. presence). Call 267-941-1099 (6 a.m.-11 p.m. ET); get EIN immediately, but may need to fax signed form.
Fax: Send to 855-641-6935 (U.S.) or other numbers for international; receive EIN in about 4 business days.
Mail: Send to IRS EIN Operation in Cincinnati, OH; allow 4-5 weeks.

Processing times vary: immediate for online/phone, 4 days for fax, 4-5 weeks for mail. Limit: One EIN per responsible party per day.

What Happens After Submitting: Receiving Your EIN Letter

Upon approval, you’ll receive your EIN immediately (online/phone) or via fax/mail. The official confirmation is CP 575, the EIN assignment notice, which includes your EIN, legal name, and address. Print and store it securely—it’s proof of your EIN for banking, tax filings, and more.

If applying via third-party designee, they may receive the EIN, but the notice is mailed to you. Keep records permanent, as the EIN is lifelong unless your entity changes significantly (e.g., from sole prop to corporation, requiring a new EIN). Report changes like address or responsible party using Form 8822-B within 60 days.

If you lose your EIN letter, request a replacement by calling the IRS Business & Specialty Tax Line at 800-829-4933.

FAQs About SS-4 and EIN Applications

How long does it take to get an EIN? Immediate online; 4 days fax; 4-5 weeks mail.
Is there a fee for an EIN? No—it’s free from the IRS. Beware of scam sites charging fees.
Can I apply for an EIN before forming my business? Form your entity (e.g., LLC) with your state first to avoid delays.
What if I already have an EIN? Use the existing one; apply for a new only if your business structure changes fundamentally.
Do foreign entities need an EIN? Yes, for U.S. tax obligations; use phone, fax, or mail.

Applying for an EIN via Form SS-4 is a straightforward process that sets the foundation for your business’s tax and financial operations. By following this guide and using official IRS methods, you can avoid common pitfalls and receive your EIN letter efficiently. For complex situations, consult a tax professional. Start your application now at IRS.gov to get your business on the right track—remember, it’s free and fast online! If you have questions, refer to the latest IRS instructions for the most current details.