You fill out IRS Form SS-4 by entering your legal name, mailing address, responsible party, entity type, reason for applying, start date, and expected employee and tax details, then submitting it online, by fax, by mail, or by international phone to receive an Employer Identification Number (EIN). The EIN is the nine-digit federal tax ID the Internal Revenue Service uses to track a business, trust, estate, nonprofit, or household employer for federal tax purposes.
Most filers get an EIN in minutes through the online EIN application, but a single wrong entry on Line 7b, Line 8a, or Line 9a can delay your filing for weeks, trigger backup withholding, or block you from opening a business bank account. According to the IRS Data Book, the IRS issued more than 5.4 million EINs in fiscal year 2023, and rejected applications often stem from mismatched names, duplicate responsible-party requests, or incorrect entity classification.
Here is what you will learn in this guide:
- 📋 The exact line-by-line walkthrough of every box on Form SS-4 with real examples
- 🏢 Which entity type to select if you run an LLC, corporation, partnership, trust, estate, or nonprofit
- 🌍 How foreign applicants without a Social Security Number or ITIN can still apply
- ⚠️ The most common SS-4 mistakes that delay your EIN and how to avoid each one
- 📞 How to call the IRS, fax, mail, or apply online — and which method is fastest for your situation
What Is IRS Form SS-4?
Form SS-4, Application for Employer Identification Number, is the official federal form used to request an EIN from the IRS. The EIN is a nine-digit number formatted as XX-XXXXXXX, and it functions like a Social Security Number for a business or other tax entity. The legal authority for the EIN comes from Internal Revenue Code §6109 and the related Treasury Regulation §301.6109-1, which require taxpayers to furnish identifying numbers on returns and statements.
The plain-English meaning is simple: if you run a business, hire employees, open a business bank account, form a trust, settle an estate, or operate a nonprofit, the IRS needs a way to identify your tax filings, and Form SS-4 starts that process. The consequence of skipping it is real, because banks will refuse to open business accounts without an EIN, payroll cannot be processed, and certain tax returns cannot be filed at all.
A real example helps: Maria opens a small bakery as a single-member LLC in Austin, Texas. She wants to open a business checking account at her local bank, but the banker tells her the federal Customer Identification Program rules require an EIN before the account opens. Maria submits Form SS-4 online, gets her EIN that same afternoon, and walks back to the bank the next morning to finish the account opening.
A common misconception is that sole proprietors with no employees do not need an EIN. While true under IRS sole proprietor rules, most banks, payment processors, and 1099 payers still ask for one to avoid using your SSN on every form, so getting an EIN protects your privacy.
Who Issues the EIN
The IRS issues every EIN through its Business and Specialty Tax Line and through its online EIN assistant. No state agency issues federal EINs, and no third-party service has special access. Many third-party filing services charge $200 or more to file a free form, which is a frequent source of consumer complaints filed with the Federal Trade Commission.
The consequence of paying a third-party service is mostly financial, because the IRS charges no fee, and the online application takes about 15 minutes. The misconception that the IRS will reject self-filed applications is false, since over 95% of EINs are self-issued without professional help.
When You Must File Form SS-4
You must file Form SS-4 before you file your first federal tax return, before you hire your first employee, before you open a business bank account, and before you operate as a corporation, partnership, multi-member LLC, trust, or estate. The IRS recommends applying four to five weeks before you actually need the EIN, although online applications are usually instant.
The consequence of waiting too long is that you may have to file paper returns and write “Applied For” in the EIN box, which slows IRS processing and can delay refunds. David, an executor of his late father’s estate, learned this the hard way when he tried to sell estate property without an EIN and the title company refused to close until the estate had its own tax ID.
Who Needs an EIN and Why
Almost every entity that is not a single-owner sole proprietor with no employees needs an EIN. The IRS EIN eligibility list covers employers, corporations, partnerships, multi-member LLCs, trusts (except certain grantor-owned revocable trusts), estates, real estate mortgage investment conduits, nonprofits, farmers’ cooperatives, plan administrators, and household employers paying domestic workers.
The “why” behind this rule is rooted in IRC §6109(a), which requires unique taxpayer identifiers so the IRS can match wage statements, information returns, and tax payments to the correct entity. Without that match, withheld taxes get lost, refunds are delayed, and the IRS may issue a CP575 notice to a wrong entity.
A real-world example: Aisha moves to the United States from Kenya and forms a Delaware C-corporation to run an e-commerce business. She has no SSN or ITIN yet, so she cannot use the online application. She faxes Form SS-4 to the IRS international fax line listed in the form instructions, writes “Foreign” on Line 7b, and receives her EIN by return fax in about four business days.
A common misconception is that single-member LLCs always need an EIN. They do not, unless they have employees, file excise taxes, or elect corporate taxation under Form 8832. However, almost every bank requires one anyway.
Sole Proprietors and Single-Member LLCs
A sole proprietor with no employees and no excise tax filings can use a Social Security Number for federal tax purposes. The same is true for a single-member LLC that has not elected corporate tax treatment, because it is a “disregarded entity” under Treasury Regulation §301.7701-3.
The consequence of skipping the EIN is that every 1099-NEC, W-9, and bank form lists your personal SSN, which raises identity-theft risk. Carlos, a freelance graphic designer, kept giving clients his SSN until one client suffered a data breach and his identity was stolen, costing him months of Identity Theft Affidavit work.
Corporations, Partnerships, and Multi-Member LLCs
Every C-corporation, S-corporation, partnership, and multi-member LLC must have an EIN from day one because each must file an annual return on Form 1120, Form 1120-S, or Form 1065. The consequence of filing without one is automatic processing delays and possible late-filing penalties under IRC §6651.
A misconception is that an S-corp election on Form 2553 replaces the EIN application. It does not, because Form 2553 requires the EIN to be entered at the top.
Trusts, Estates, and Nonprofits
Most trusts, all estates with gross income over $600, and every 501(c) nonprofit must have an EIN. Estates need an EIN before the executor can open an estate bank account, sell estate property, or file Form 1041. Nonprofits need an EIN before they file Form 1023 for 501(c)(3) recognition.
The consequence of skipping the EIN for a nonprofit is that the IRS will not process the exemption application, donors cannot claim deductions, and grant funders will refuse to release funds.
Household Employers and Foreign Applicants
If you pay a nanny, housekeeper, or home health aide $2,700 or more in 2026 (the 2026 Schedule H threshold), you are a household employer who must file Schedule H and need an EIN. Foreign applicants without an SSN or ITIN can still get an EIN by faxing or calling the IRS international line at +1-267-941-1099, as detailed in the Form SS-4 instructions.
Line-by-Line Walkthrough of Form SS-4
The current SS-4 has 18 numbered lines plus signature blocks, and every entry matters. Below is a complete walkthrough using a running example: Greenleaf Bakery LLC, a multi-member LLC owned by Maria and her sister, opening on June 1, 2026, in Austin, Texas, with two expected employees.
Line 1 — Legal Name of Entity or Individual
Enter the exact legal name as it appears on your formation document, such as the Texas Certificate of Formation or the IRS-recognized trust instrument. For Greenleaf Bakery LLC, Maria writes “Greenleaf Bakery LLC” exactly as filed with the Texas Secretary of State.
The consequence of a mismatch is that the IRS may issue the EIN under a slightly different name, causing your future 1120, 1065, or 941 filings to bounce. A common misconception is that you can use a “doing business as” name on Line 1; you cannot, because Line 2 exists for that purpose.
Line 2 — Trade Name (DBA)
Enter the “doing business as” or trade name only if it differs from Line 1. If Greenleaf Bakery LLC also operates a kiosk under “Greenleaf Express,” that goes here. Leave blank if you have no DBA.
The consequence of putting the DBA on Line 1 instead of Line 2 is a name-control mismatch on every future return. The IRS uses the first four letters of the Line 1 name to build the name control.
Line 3 — Executor, Administrator, Trustee, “Care of” Name
Use this line only for trusts and estates. Enter the trustee or executor’s name. For David’s late father’s estate, David writes “David Smith, Executor.”
A misconception is that this line is optional for estates. It is not, because the Form 1041 instructions require the responsible fiduciary’s name to match.
Lines 4a-4b — Mailing Address
Enter the mailing address where the IRS should send EIN correspondence, including the CP575 confirmation notice. Use a U.S. address if you have one. Foreign addresses are allowed.
The consequence of an outdated address is that the CP575, which lenders and banks frequently demand, never arrives, and obtaining a replacement 147C letter requires a phone call and an hour of hold time.
Lines 5a-5b — Street Address (If Different)
Enter the physical street address only if different from Line 4. P.O. boxes are not allowed here.
Line 6 — County and State of Principal Business
Enter the county and state where the business is principally located. For Greenleaf Bakery LLC, Maria writes “Travis County, TX.”
Line 7a — Responsible Party Name
This is one of the most regulated lines on the form. The “responsible party” must be a natural person who controls, manages, or directs the entity, per the 2014 IRS update on responsible party rules. Entities cannot be responsible parties (except for government entities).
The consequence of listing a “nominee” (a placeholder owner like a registered agent or filing service) is that the IRS considers it fraudulent, and the EIN can be revoked. Aisha learned this when her formation service offered to be the “responsible party”; she correctly refused and listed herself.
Line 7b — Responsible Party SSN, ITIN, or EIN
Enter the SSN or ITIN of the natural person on Line 7a. If the person has neither (a foreign applicant), write “Foreign” in this field. The online EIN application will not work without an SSN or ITIN, so foreign applicants must use fax, mail, or phone.
A misconception is that you can use the entity’s own EIN here. You cannot, because the IRS requires a personal identifier of a human being.
Line 8a — Is This Application for an LLC?
Check “Yes” if the entity is an LLC, including a single-member LLC. Otherwise check “No.”
Line 8b — Number of LLC Members
Enter the number of members. For Greenleaf Bakery LLC, Maria writes “2.”
Line 8c — Was the LLC Organized in the United States?
Check “Yes” if formed under U.S. state law, even if owned by foreign persons.
Line 9a — Type of Entity
Choose exactly one box: Sole proprietor, Partnership, Corporation (with form number), Personal service corp, Church, Other nonprofit, Estate, Plan administrator, Trust, Military, Farmers’ cooperative, REMIC, State/local government, Federal government, Indian tribal government, or Other (specify).
The consequence of picking the wrong box is significant: a multi-member LLC that wants to be taxed as a partnership should check “Partnership” here, not “Corporation,” even though the entity is legally an LLC. To be taxed as a corporation, the LLC must also file Form 8832 or Form 2553.
A misconception is that “Other” is a safe default. It is not, because writing “LLC” on the Other line triggers IRS letter LTR 147C asking you to clarify, delaying you weeks.
Line 9b — State or Foreign Country of Incorporation
Enter the state or country where the entity was legally formed. For Greenleaf Bakery LLC, that is “Texas.” For Aisha’s Delaware C-corp, that is “Delaware.”
Line 10 — Reason for Applying
Choose one: Started new business, Hired employees, Banking purposes, Changed type of organization, Purchased going business, Created a trust, Created a pension plan, or Other (specify). For Greenleaf Bakery LLC, Maria checks “Started new business” and writes “Retail bakery.”
The consequence of checking the wrong reason is mostly cosmetic, but “Banking purposes” alone for a true operating business can trigger an IRS classification mismatch.
Line 11 — Date Business Started or Acquired
Enter the legal start date of the business or the date the trust or estate was created. For Greenleaf Bakery LLC, Maria writes “06/01/2026.”
A misconception is that this must be the date you signed the form. It is not — it is the date the entity legally began existing.
Line 12 — Closing Month of Accounting Year
Most calendar-year filers write “December.” Some entities, like personal service corporations, are restricted under IRC §441 and must use a calendar year unless they qualify for a fiscal year.
Line 13 — Highest Number of Employees Expected in Next 12 Months
Break down the number into three categories: Agricultural, Household, and Other. For Greenleaf Bakery LLC, Maria writes “0, 0, 2.”
Line 14 — Form 944 Eligibility
If your annual employment tax liability will be $1,000 or less, check the box to file Form 944 annually instead of Form 941 quarterly. The consequence of incorrectly checking this box is that the IRS will reject your quarterly 941 filings until you formally request a switch.
Line 15 — First Date Wages Will Be Paid
Enter the first date you expect to pay wages, even if approximate. Leave blank if you do not plan to pay wages.
Line 16 — Principal Activity
Choose one: Construction, Real estate, Rental and leasing, Manufacturing, Transportation and warehousing, Finance and insurance, Health care and social assistance, Accommodation and food service, Wholesale, Retail, or Other. Greenleaf Bakery LLC checks “Accommodation and food service.”
Line 17 — Principal Line of Merchandise or Services
Briefly describe what you sell or do. Maria writes “Retail bakery selling bread and pastries.”
Line 18 — Prior EIN Applications
Check “Yes” if the responsible party or entity has ever applied for an EIN before, and provide the prior EIN. Check “No” otherwise. The consequence of checking “No” when you have a prior EIN can trigger an IRS investigation under IRC §7206 for false statements.
Third-Party Designee and Signature
The third-party designee box lets you authorize a CPA or attorney to receive the EIN on your behalf. The signature block must be signed by the responsible party listed on Line 7a, not by a nominee or filing service. An unsigned mailed or faxed SS-4 will be rejected outright.
How to File Form SS-4: Four Methods
The IRS accepts Form SS-4 four ways, and each has different processing times, eligibility rules, and consequences. The fastest method for U.S. applicants is online, while foreign applicants must use fax, mail, or phone.
Method 1 — Online EIN Application
Go to the IRS online EIN application between 7 a.m. and 10 p.m. Eastern Time, Monday through Friday. The system issues an EIN immediately upon completion. The responsible party must have a valid SSN or ITIN, and only one EIN per responsible party per day is allowed under the 2012 IRS limitation.
The consequence of trying to apply twice in one day is an automatic system block and a wasted hour. Maria completed the online application in 12 minutes and downloaded her EIN confirmation letter on the spot.
Method 2 — Fax
Fax Form SS-4 to the appropriate IRS fax number listed in the Form SS-4 instructions. U.S. applicants fax to 855-641-6935. Foreign applicants fax to 855-215-1627. Processing takes about four business days, and the IRS faxes the EIN back if you provide a return fax number.
Method 3 — Mail
Mail to the address in the form instructions. Processing takes four to five weeks. The consequence of mailing during peak season is that returns can be delayed, especially in February and March.
Method 4 — International Phone
Foreign applicants without an SSN or ITIN can call +1-267-941-1099 between 6 a.m. and 11 p.m. Eastern Time, Monday through Friday, to obtain an EIN by phone. Aisha used this method and received her EIN in a 25-minute call.
Three Common SS-4 Scenarios
Every applicant fits a common pattern, and each pattern has its own pitfalls. The three most common scenarios are a new LLC, a new estate, and a foreign-owned corporation.
Scenario Tables
| Filing Step for New LLC | Outcome |
|---|---|
| Maria forms Greenleaf Bakery LLC in Texas with her sister | Multi-member LLC must file Form 1065 |
| She applies online, lists herself as responsible party | EIN issued instantly, valid for banking |
| She checks Line 9a “Partnership” not “Corporation” | LLC defaults to partnership tax treatment |
| She does not file Form 8832 | LLC stays a partnership for tax |
| She receives CP575 by mail in 10 days | Permanent EIN confirmation for lenders |
| Filing Step for New Estate | Outcome |
|---|---|
| David’s father dies in March 2026 | Estate exists as of date of death |
| David is named executor in the will | David becomes responsible party |
| He fills SS-4 with “David Smith, Executor” on Line 3 | IRS recognizes fiduciary capacity |
| He checks “Estate” on Line 9a | EIN issued under estate, not personal SSN |
| He opens an estate bank account with the EIN | Probate proceeds, taxes filed on Form 1041 |
| Filing Step for Foreign-Owned C-Corp | Outcome |
|---|---|
| Aisha forms Delaware C-corp from Nairobi | Entity legally exists under Delaware law |
| She has no SSN or ITIN | Online application unavailable |
| She writes “Foreign” on Line 7b | IRS accepts foreign responsible party |
| She faxes SS-4 to 855-215-1627 | Processing in four business days |
| She receives EIN by return fax | Can open U.S. bank account, file Form 1120 |
Mistakes to Avoid
Avoiding mistakes on Form SS-4 saves weeks of delay and prevents IRS letters that demand corrections.
- Listing a registered agent or formation service as the responsible party, which the IRS treats as a nominee filing and may revoke
- Applying for two EINs in one day under the same responsible party, which violates the IRS daily limit and blocks both applications
- Using a DBA on Line 1 instead of the legal name, which causes name-control mismatches on every future return
- Checking “Corporation” on Line 9a for an LLC that wants partnership taxation, which forces a corrected Form 8832 filing
- Leaving Line 7b blank instead of writing “Foreign” when the responsible party has no SSN or ITIN
- Forgetting to sign the form before faxing or mailing, which causes automatic rejection
- Paying a third-party service $200 or more for a free IRS process
- Writing the wrong start date on Line 11, which can misalign the entity’s first tax year
- Checking Line 14 (Form 944) when annual employment tax will exceed $1,000, triggering rejected 941 filings
- Failing to keep the CP575 letter, since the IRS will not reissue it and you must request a 147C replacement letter by phone
Do’s and Don’ts
These rules separate clean filings from rejected ones.
- Do list a natural person on Line 7a who actually controls the entity
- Do match Line 1 exactly to your state formation document
- Do apply online if you have an SSN or ITIN, since it is fastest
- Do save the CP575 confirmation in two separate locations
- Do file Form 8822-B within 60 days if your responsible party changes
- Don’t use a nominee as responsible party, because the IRS may revoke the EIN
- Don’t pay a third-party service for a free IRS form
- Don’t apply for multiple EINs in one day under the same responsible party
- Don’t write “LLC” on the Line 9a “Other” line, because it triggers IRS letter 147C
- Don’t lose the CP575, because banks and the SBA frequently demand it
Pros and Cons of Each Filing Method
Each filing method fits a different situation.
- Online: Pro — instant EIN; Con — requires SSN or ITIN
- Fax: Pro — open to foreign applicants; Con — four-business-day wait
- Mail: Pro — works for any applicant; Con — four to five week wait
- Phone: Pro — only option for some foreign applicants; Con — long hold times
- Third-party designee: Pro — CPA can handle filing; Con — extra Form 2848 paperwork
Federal Law First, Then State Nuances
Federal law under IRC §6109 governs the EIN itself, but every state adds its own tax registration requirements after you receive the federal EIN. California requires a separate California Employer Account Number from the EDD. New York requires registration with the NYS Department of Taxation and Finance. Texas does not have a state income tax but requires a Texas Sales and Use Tax Permit. Florida requires a Florida Reemployment Tax Account once you hire employees.
The consequence of skipping state registration is steep: California assesses penalties under CUIC §1112, and New York assesses interest and late-filing penalties on every quarter missed.
Court Rulings That Shape Responsible Party Rules
In United States v. Boyle, 469 U.S. 241 (1985), the Supreme Court held that taxpayers cannot delegate their filing duties to a third party to avoid penalties, which directly underpins the IRS rule that the responsible party must be a real person who actually controls the entity. In United States v. Galletti, 541 U.S. 114 (2004), the Court confirmed that partnership-level employment tax assessments bind the underlying partners, reinforcing why the SS-4 responsible party designation has lasting personal consequences.
These rulings explain why the IRS limits responsible-party flexibility, and why nominee filings are treated so harshly. The consequence of ignoring them is that personal liability can attach even years after the EIN issues.
FAQs
Do I need a new EIN if I change my business name?
No. A name change alone does not require a new EIN. File Form 8822-B within 60 days, or check the name-change box on your next annual return.
Can a single-member LLC use the owner’s SSN instead of an EIN?
Yes. A single-member LLC with no employees and no excise tax may use the owner’s SSN. Most banks still require an EIN to open business accounts.
Can a non-U.S. citizen apply for an EIN?
Yes. Foreign applicants without an SSN or ITIN can apply by fax, mail, or by calling +1-267-941-1099. Online applications require an SSN or ITIN.
Do I need a new EIN if I convert from sole proprietor to LLC?
Yes. A change in entity structure usually requires a new EIN under IRS guidance on EIN changes. The old EIN cannot follow the new entity.
Is there a fee to apply for an EIN?
No. The IRS charges no fee. Third-party services that charge $100 to $300 for filing are not affiliated with the IRS.
Can I get an EIN the same day?
Yes. The online EIN application issues an EIN immediately for U.S. applicants with an SSN or ITIN, between 7 a.m. and 10 p.m. Eastern.
Do trusts always need an EIN?
No. Revocable grantor trusts often use the grantor’s SSN under Treasury Reg §1.671-4. Irrevocable trusts and trusts after the grantor’s death require an EIN.
Can the responsible party be a corporation or LLC?
No. The responsible party must be a natural person, except for certain government entities, per 2014 IRS responsible party rules.
Can I apply for more than one EIN per day?
No. Since 2012, the IRS limits responsible parties to one EIN per day across all methods to prevent abuse and streamline processing.
What is the CP575 letter?
Yes, it matters — the CP575 confirmation notice is the official IRS letter confirming your EIN. Keep it permanently because the IRS will not reissue it.
Do I need an EIN to open a business bank account?
Yes. Almost every U.S. bank requires an EIN under federal Customer Identification Program rules, even for single-member LLCs that could otherwise use an SSN.
Can I cancel an EIN once issued?
No. EINs are permanent and never reused. You can only close the IRS business account by mailing a letter, as described in IRS canceling an EIN guidance.
Related reading
- Speak With a Live IRS Agent
- How to Fill Out Form 2553 (w/Examples) + FAQs
- How to Get EIN as a Household Employer (w/Examples) + FAQs
- How to Fill Out Form SSA-1694 (w/Examples) + FAQs
- How to Fill Out IRS Form W-9 (w/Examples) + FAQs
- How to Fill Out IRS Form 14039-B (w/Examples) + FAQs
- How to Fill Out IRS Form 8300 (w/Examples) + FAQs