Updated October 16, 2026. Quick answer: Form SS-4 is the Application for Employer Identification Number. The instructions say to use it to apply for an EIN, and the form says to file it if the applicant entity doesn’t already have an EIN but is required to show one on a return, statement or other document. The decisions are the entity type on line 9a, the responsible party on line 7, and which way to apply.
More IRS forms and schedules for individual filers, read line by line: Schedule H instructions and Schedule H Part II FUTA tax.
More IRS forms for employers and business owners, read line by line: Form 940 instructions, Form 944 instructions and Form 720 instructions.
IRS trust and estate tax forms, read line by line: Form 1041-ES payment vouchers, Form 8855 Part I and Form 8855 Parts II and III.
IRS estate-administration forms, read line by line: Form 56 Part I and Form 8971 Part I.
More IRS forms and schedules, read line by line: Form W-3 instructions.
What Form SS-4 is for
The form’s title is “Application for Employer Identification Number”. The instructions state the purpose directly: “Use Form SS-4 to apply for an EIN.” The number’s role is also defined: “The information you provide on this form will establish your business tax account.”
An EIN has a limited use. “An EIN is for use in connection with your business activities only.” The sentence continues with a warning: “Don’t use your EIN in place of your social security number (SSN) or individual taxpayer identification number (ITIN).”
Key numbers at a glance
The figures that matter most are collected below as the form and its instructions print them.
| Item | As printed |
|---|---|
| What an EIN is | “An EIN is a 9digit number (for example, 12-3456789) assigned to sole proprietors, corporations, partnerships, estates, trusts, and other entities for tax filing and reporting purposes.” |
| One per day | “To ensure fair and equitable treatment for all taxpayers, EIN issuances are limited to one per responsible party, per day.” |
| Responsible party changes | “Changes in responsible parties must be reported to the IRS within 60 days.” |
| Partnership terminated by sale | “terminated its partnership status because at least 50% of the total interests in partnership capital and profits were sold or exchanged within a 12month period.” |
| Form 944 election | “Your employment tax liability will generally be $1,000 or less if you expect to pay $5,000 or less in total wages subject to social security and Medicare taxes and federal income tax withholding.” |
Who needs an EIN
The form’s page 2 begins the test: “File Form SS-4 if the applicant entity doesn’t already have an EIN but is required to show an EIN on any return, statement, or other document.”
The footnote gives examples for sole proprietors: “For example, a sole proprietorship or selfemployed farmer who establishes a qualified retirement plan, or is required to file excise, employment, alcohol, tobacco, or firearms returns, must have an EIN.” Entities fare differently: “A partnership, corporation, REMIC (real estate mortgage investment conduit), nonprofit organization (church, club, etc.), or farmers’ cooperative must use an EIN for any taxrelated purpose even if the entity doesn’t have employees.”
Starting a business, hiring and banking each have a reason-for-applying box on line 10. “Check this box if you’re starting a new business that requires an EIN.” “Check this box if the existing business is requesting an EIN because it has hired or is hiring employees and is therefore required to file employment tax returns.” The practical order of operations for a new LLC is walked through on the how to get an EIN page, and the bank side is on the small LLC business bank account page.
When a new EIN is not needed
Several situations look like they need a new number and do not. “Generally, a sole proprietor should file only one Form SS-4 and needs only one EIN, regardless of the number of businesses operated as a sole proprietorship or trade names under which a business operates.”
The instructions also say “Don’t apply if you already have an EIN and are only adding another place of business.” and “Don’t apply if you already have an EIN and are only hiring employees.”
The page 2 footnote lists changes that keep the existing number. It begins “However, don’t apply for a new EIN if the existing entity only (a) changed its business name, (b) elected on Form 8832 to change the way it is taxed (or is covered by the default rules), or (c)” and ends with the partnership case in the table above. For an S election, “An existing corporation that is electing or revoking S corporation status should use its previously assigned EIN.” The late election path is on the late S corporation election page.
A change of structure is different. “However, if a sole proprietorship incorporates or enters into a partnership, a new EIN is required.” “Also, each corporation in an affiliated group must have its own EIN.”
Lines 1 to 6: names and addresses
Line 1 takes the legal name. “Enter the legal name of the entity (or individual) applying for the EIN exactly as it appears on the social security card, charter, or other applicable legal document.” For a sole proprietor the rule is “If you’re a sole proprietor, enter your individual name, not your business name.” “Enter your business name on line 2.”
Names should stay consistent afterwards. “To prevent processing delays and errors, use only the legal name (or the trade name) on all tax returns.” Addresses follow the line: mailing address on lines 4a and 4b, a physical address on lines 5a and 5b only when different, and the county and state of the principal business on line 6.
Line 7: the responsible party
The responsible party is an individual, with limited exceptions. “Unless the applicant is a government entity, the responsible party must be an individual (that is, a natural person), not an entity.”
The instructions define the role by control: “The person identified as the responsible party should have a level of control over, or entitlement to, the funds or assets in the entity that, as a practical matter, enables the person, directly or indirectly, to control, manage, or direct the entity and the disposition of its funds and assets.”
The number to enter is also specified: “Otherwise, you must enter an SSN or ITIN on line 7b.” Changes after the EIN is issued are reported on a separate form: “Use Form 8822-B to report changes to your responsible party, address or location.”
Lines 8 and 9: LLCs and entity types
Line 8a asks about LLCs, and the instructions explain the tax meaning. “For federal tax purposes, an LLC may be treated as a partnership or corporation or be disregarded as an entity separate from its owner.” Line 9a then asks for the entity type, and the form says “Type of entity (check only one box).”
| Entity | As printed in the instructions |
|---|---|
| Sole proprietor | “Check this box if you file Schedule C or Schedule F (Form 1040) and have a qualified plan, or are required to file excise, employment, alcohol, tobacco, or firearms returns, or are a payer of gambling winnings.” |
| Corporation | “This box is for any corporation other than a personal service corporation.” |
| Estate | “An estate is a legal entity created as a result of a person’s death.” |
| Trust | “For trusts, the responsible party is a grantor, owner, or trustor.” |
| LLC, single member | “By default, a domestic LLC with only one member is disregarded as an entity separate from its owner and must include all of its income and expenses on the owner’s tax return (for example, Schedule C (Form 1040)).” |
| LLC, two or more members | “Also, by default, a domestic LLC with two or more members is treated as a partnership.” |
| Other | “If not specifically listed, check the Other box and enter the type of entity and the type of return, if any, that will be filed” |
An LLC can change its default treatment. “A domestic LLC may file Form 8832 to avoid either default classification and elect to be classified as an association taxable as a corporation.” Whether to form an LLC at all is covered on the page on whether you need an LLC, and a rental property owner’s version of the question is on the LLC for rental property page.
Ways to apply and how long each takes
The instructions allow four routes, with a geographic limit on two of them. “You can apply for an EIN online (only for applicants in the United States or U.S. territories), by telephone (only for applicants outside of the United States or U.S. territories), by fax, or by mail, depending on how soon you need to use the EIN.”
| Route | As printed in the instructions |
|---|---|
| Recommended route | “The IRS recommends that you apply for your EIN electronically, if possible.” |
| Online | “you can receive an EIN online and use it immediately to file a return or make a payment.” |
| Fax | “Under the Fax-TIN program, you can receive your EIN by fax generally within 4 business days.” |
| “Complete Form SS-4 at least 4 to 5 weeks before you will need an EIN.” | |
| Mail timing | “You will receive your EIN in the mail in approximately 4 weeks.” |
| Telephone | “The IRS no longer issues EINs by telephone for domestic taxpayers.” |
Online applicants need a number of their own: “The principal officer, general partner, grantor, owner, trustor, etc., must have a valid taxpayer identification number (SSN, EIN, or ITIN) in order to use the online application.”
Duplicates are discouraged: “Use only one method for each entity so you don’t receive more than one EIN for an entity.”
Hiring, Form 944 and signing
Lines 13 and 14 apply to employers. Line 14 offers the annual alternative to the quarterly return: “If you expect your employment tax liability to be $1,000 or less in a full calendar year, you’re eligible to file Form 944 annually (once each year) instead of filing Form 941 quarterly (every 3 months).” Once chosen, the choice sticks: “Once you check the box, you must continue to file Form 944, regardless of the amount of tax shown on your return, until the IRS instructs you to file Form 941.”
Employers must also deposit electronically: “You must make electronic deposits of all depository taxes (such as employment tax, excise tax, and corporate income tax) using EFTPS.”
The signature declaration reads “Under penalties of perjury, I declare that I have examined this application, and to the best of my knowledge and belief, it is true, correct, and complete.” On completeness, “We will be unable to issue an EIN to you unless you provide all of the requested information that applies to your entity.” An executor’s separate need for a number is covered on the estate EIN and bank account page.
Which revision applies
The edition read for this page is Form SS-4 (Rev. December 2025) and the Instructions for Form SS-4 (Rev. December 2025), which are the revisions irs.gov served when they were read on 2026-10-16. Check the revision printed on the form you are filing, because a later revision can change the ways to apply, the timing and the line layout.
Common mistakes
- Applying for a second EIN when the entity only changed its name. The instructions say not to apply for a new EIN if the existing entity only changed its business name or elected a new tax treatment on Form 8832.
- Putting a company name on the responsible party line. The instructions say that unless the applicant is a government entity, the responsible party must be an individual, not an entity.
- Applying more than one way for the same entity. The instructions say to use only one method for each entity so that the entity does not receive more than one EIN.
Related: how to get an EIN, do you need an LLC, estate EIN and bank account, business bank account for a small LLC, and Form 1041 for estates.
Sources
- Form SS-4 (Rev. December 2025), Application for Employer Identification Number: https://www.irs.gov/pub/irs-pdf/fss4.pdf
- Instructions for Form SS-4 (Rev. December 2025): https://www.irs.gov/pub/irs-pdf/iss4.pdf
Read from the IRS documents linked above on October 16, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.