If you plan to open a business bank account, hire employees, or file your taxes, you will likely encounter Form SS-4, which is used to obtain an employer identification number (EIN) from the IRS.
The SS4 is an important document that provides the federal government with confirmation that you are operating your business legitimately. This guide will help explain what this form is used for, why you need it, and how to complete it.
What is Form SS-4?
An SS4 form is a document from the Internal Revenue Service (IRS), officially titled “Application for Employer Identification Number.” It enables businesses—including sole proprietors, corporations, partnerships, estates, trusts, and other entities—to apply for a unique tax identification number (TIN), called an EIN.
Just as an individual needs a Social Security number (SSN) for identification, your business needs its own TIN for tax purposes. Whether you apply online, by mail, or by fax with your completed SS4 form, the goal is the same: register your business with the IRS and get the EIN you need for taxes and banking.
Once your business’s EIN is assigned, this nine-digit number stays with your business entity for its lifetime. You will use it on tax returns, when hiring employees, and for business banking purposes. Even if your venture is a sole proprietorship with no employees, having an EIN helps protect your personal identity because it allows you to keep your Social Security number private.
Most businesses will need an EIN at some point. In general, you need to obtain one if you want to:
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Hire employees. To remit employment taxes, you must have an EIN.
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Operate as a partnership, multimember LLC, or corporation. These entity types are legally required to have a federal tax ID.
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File tax returns. This is specifically for employment taxes, excise taxes, or alcohol, tobacco, and firearms returns.
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Have a self-employed retirement plan. If you have any type of self-employed retirement plan, such as a self-employed pension (SEP) IRA or Keogh plan, you will need an EIN.
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Open business bank accounts. Banks require you to provide an EIN to open an account in the business name.
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Apply for business licenses. Local and state permits often require this number on business license applications.
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Become involved with other entities. If you perform services for a trust, estate, or non-profit organization as a contractor, they will need your TIN to file form 1099. While you can use your Social Security number, using an EIN allows you to keep your SSN private when filling out vendor forms.
Even if you’re a sole proprietor, your accountant may recommend getting an EIN to separate your personal financial activities from your business activities.
What information must you include on Form SS-4?
- Line 1: Legal name of entity (or individual) for whom the SS4 is being requested
- Line 2: Trade name of business (if different from name on line 1)
- Line 3: Executor, administrator, trustee, “care of” name
- Lines 4-6: Mailing address and street address
- Lines 7-9: Responsible party and type
- Line 8: Limited liability company (LLC) info
- Line 9a: Type of entity
- Line 9b: State or foreign country where incorporated
- Line 10: Reason for applying
- Line 11: Date business started or acquired
- Line 12: Closing month of accounting year
- Line 13: Highest number of employees expected in the next 12 months
- Line 14: Employment tax liability
- Line 15: First date wages or annuities were paid
- Line 16: Principal activity
- Line 17: Description of principal line of merchandise/service
- Line 18: Has the applicant entity ever applied for and received an EIN?
- Third party designee
- Signature block
IRS Form SS-4 is a single-page document that asks for specific details about your business. Here’s a breakdown of the sections you will need to complete:
Line 1: Legal name of entity (or individual) for whom the SS4 is being requested
This is the exact legal name of the business as it appears on your formation documents (i.e., articles of incorporation). If you are a sole proprietor, this is your full legal name. If you are a trust, it is the legal name of the trust. Do not abbreviate unless the abbreviation is part of the legal name.
Line 2: Trade name of business (if different from name on line 1)
This is your “doing business as” (DBA) or fictitious business name. If you don’t use a separate trade name, leave this blank.
Line 3: Executor, administrator, trustee, “care of” name
If the IRS sends mail to your business or entity, to whose specific attention should it be addressed? Businesses usually leave this blank, unless they want mail sent to a specific officer.
Lines 4-6: Mailing address and street address
Line 4 asks for your mailing address, which is where the IRS will send mail like tax forms and notices. This can be a P.O. box or third-party address, like your accountant’s office. If your actual business location is different from where you receive mail, you must also fill in the street address on line 5. Note that the street address must be a physical location; you can’t use a P.O. box here.
Lines 7-9: Responsible party and type
The IRS requires you to list a single responsible party who controls or manages the entity. If the business has multiple owners (such as equal partners), you must select one individual to list there. This person must have a Social Security number or individual taxpayer identification number (ITIN). You cannot list another company as the responsible party.
Line 8: Limited liability company (LLC) info
Fill in whether the application is for a limited liability corporation (LLC). If you’re not, check the no box. If you check yes, enter the number of LLC members. For single-member LLCs, write the number one. The form also asks if the LLC was organized in the US. If it was, check yes.
Line 9a: Type of entity
This line tells the IRS how your business is taxed. Do not leave this blank, even if you identified as an LLC in line 8. Because the IRS does not have a specific tax category for LLCs, you must check the box that matches your tax treatment. Single-member LLCs generally check “other” and write “disregarded entity.” Multimember LLCs generally check “partnership.” LLCs that elect to be taxed as S corporations check “corporation” and write 1120S in the space provided.
Line 9b: State or foreign country where incorporated
List the state or country where you filed your formation documents.
Line 10: Reason for applying
Answers include “started a new business,” “hired employees,” “compliance with IRS withholding regulations,” “banking purpose,” “created a trust/pension plan,” or other options.
Line 11: Date business started or acquired
This usually matches the date on your formation documents.
Line 12: Closing month of accounting year
For calendar year taxpayers, this is usually December. If you operate on a fiscal year schedule, which is common for some C corps or nonprofits, enter the last month of your fiscal year.
Line 13: Highest number of employees expected in the next 12 months
You must break this down by agricultural, household, and other. If you enter a number here, the IRS will expect you to file payroll tax returns.
Line 14: Employment tax liability
Will your employment tax liability be less than $1,000 for the whole year? If you entered zero employees on line 13, leave this line blank. If you do expect to have employees and your liability will be $1,000 or less, checking the box makes you eligible to file Form 944 annually instead of Form 941 quarterly.
Line 15: First date wages or annuities were paid
If you have employees, when did you (or when will you) write the first paycheck? If you have no employees, put “N/A.”
Line 16: Principal activity
Check one box that best describes the principal activity of your business. Options include:
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Construction
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Real estate
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Rental and leasing
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Manufacturing
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Health care and social assistance
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Finance and insurance
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Hospitality jobs
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Wholesale workers
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Retail
If none of the choices fit, check “none” and describe it briefly in the given space.
Line 17: Description of principal line of merchandise/service
This is a fill-in-the-blank text field that asks you to describe exactly what your business does. You’ll need to elaborate on the category you checked in line 16. The IRS uses this to assign your business a specific North American Industry Classification System (NAICS) code for statistical purposes.
Line 18: Has the applicant entity ever applied for and received an EIN?
If you check “yes,” you must write the previous EIN in the space provided. This applies to the business or entity, not you personally. If you have an EIN for a different business, the answer here is “no.” You only answer “yes” if this specific entity already received an EIN and you lost it or are reapplying.
Third party designee
This section allows you to authorize someone else to receive the EIN on your behalf, such as an accountant, attorney, or incorporation service that files the form for you. It gives the IRS permission to release the new EIN to this person and communicate with them about this specific form. This authority is temporary, and it expires the moment the EIN is assigned and released. It does not allow this person to talk to the IRS about your taxes later.
Signature block
The final section must be signed by the “responsible party” listed in line 7a. If that’s you, print your name and official role, sign the form, and enter your telephone number in case the IRS has questions during processing.
What is the penalty for not filing Form SS-4?
Technically, there is no direct financial penalty for failing to file Form SS-4 itself, as it is an application, not a tax return. However, failing to obtain an EIN may stall your business operations.
Without an EIN, you cannot open a business bank account or apply for necessary business licenses. This operational roadblock often creates a domino effect: because you cannot establish a business bank account, you may be forced to handle finances through personal accounts or cash. This makes it difficult to properly withhold and remit payroll taxes, potentially triggering IRS penalties for non-payment and non-filing. To ensure tax compliance, put obtaining an EIN on your to-do list.
Who is exempt from filing Form SS-4?
Not everyone needs to file this type of form. The most common exception applies to sole proprietors who:
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Don’t have any employees
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Don’t file excise or pension plan tax returns
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Don’t have a tax-deferred retirement savings plan designed for self-employed people
In these cases, the sole proprietor can use their Social Security number for tax filing and business purposes. However, many still choose to file the form to obtain an EIN for privacy reasons or to open business bank accounts that require one.
How to get an EIN using Form SS-4
You can file Form SS-4 online, by fax, or by mail. Complete it using the method that works best for you.
Apply online
The IRS website offers an online EIN application tool. This is the preferred method for most businesses whose legal residence is in the US or US territories.
Before you complete the application, keep in mind that you are required to complete the questions in one session. The session expires after 15 minutes of inactivity, so have your data ready. Upon completion, the system will generate your EIN Confirmation Notice as a PDF, meaning you will receive your EIN immediately.
File by fax
If you prefer to fill out the paper form, you can fax the completed form to the IRS. Fill out the form and sign it. Prepare a fax cover sheet that includes your callback number and fax number. Fax it to 855-641-6935. If you provide your fax number, you will typically receive your EIN by fax in about four business days.
File by mail
You can mail the completed Form SS-4 to the IRS service center. If you are in the US, you will mail it to: Internal Revenue Service
Attn EIN Operation
Cincinnati, OH
45999
This is the slowest method. It takes approximately four to five weeks for the IRS to process your application and send your EIN confirmation letter (Notice CP 575) to you via mail.
International applicants
For international applicants (e.g., a non-resident alien), you can apply by phone, fax, or mail. You can apply for only one EIN per day, regardless of the method used. Mail your completed application to the same address as above, or use the specific phone line for international applicants to obtain their EIN: +1-267-941-1099.
Mistakes to avoid when completing Form SS-4
Even small errors can lead to rejection or delays. Here are five common mistakes to avoid:
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Typos in the legal name. The name on Form SS-4 must match your state registration documents exactly. Even a missing comma or “Inc.” can cause headaches with the IRS.
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Missing or incorrect responsible party. You must list a person, not another company, as the responsible party, and you need to provide their correct SSN or ITIN.
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Using a P.O. box for street address. The IRS requires a physical street address for lines 5a and 5b.
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Incomplete dates. Ensure the business started date matches your state formation documents. Also, ensure the accounting year closing month matches the fiscal year set in your bylaws or partnership agreement.
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Forgetting to sign. If you mail or fax the form, it must have a written signature. The online applications use an electronic signature method.
SS4 form FAQ
What is an SS4 form for?
The SS4 form is the application used to apply for an employer identification number (EIN) from the IRS. It tells the government what kind of business you are running, and it allows them to assign the business a tax ID for tax compliance and banking purposes. Once you have the EIN, you are ready to move forward with opening bank accounts, hiring employees, and managing your small business taxes.
How do I obtain a copy of my SS4 form?
It’s not standard to receive a certified copy of the SS4 application from the IRS. However, after the IRS processes your Form SS-4, it will send you an EIN confirmation letter (Notice CP 575). This letter serves as official proof of your employer identification number. If you need a copy of the application itself for your own records, you should save a copy before you submit it.
Can I get a copy of my EIN letter from the IRS?
Yes, if you lost your original EIN confirmation letter, you can request a replacement letter (147C letter), which serves the same purpose. Call the IRS Business & Specialty tax line (800-829-4933), verify your identity to the agent, and they can often fax or mail the verification letter to you.
