What are the 12 core EIN terms?
The 12 core EIN terms are EIN, Form SS-4, CP-575, 147C letter, responsible party, line 7b, TIN, ITIN, SSN, third party designee, disregarded entity, and reference number 101. Each one carries its own IRS rule.
| # | Term | What it is | Key number |
|---|---|---|---|
| 1 | EIN (Employer Identification Number) | The federal tax ID the IRS assigns to a business entity | 9 digits |
| 2 | Form SS-4 | The IRS application form that produces an EIN | 18 fields |
| 3 | CP-575 | The official IRS letter confirming a newly assigned EIN | 1 per EIN |
| 4 | 147C letter | The IRS replacement confirmation for an EIN already assigned | Replaces a lost CP-575 |
| 5 | Responsible party | The individual who controls the entity and its funds | 1 per EIN |
| 6 | Line 7b | The SS-4 field that routes the application | 1 word: Foreign |
| 7 | TIN (Taxpayer Identification Number) | The umbrella term for every 9-digit US tax ID | 5 types |
| 8 | ITIN (Individual Taxpayer Identification Number) | A personal tax ID for individuals with no SSN | Begins with 9 |
| 9 | SSN (Social Security Number) | The personal number that unlocks the 15-minute online route | 15 minutes |
| 10 | Third party designee | The person the applicant authorizes to receive the EIN | Authority ends at assignment |
| 11 | Disregarded entity | A single-member LLC the IRS looks through for tax purposes | 1 member |
| 12 | Reference number 101 | The online-tool error that reports a name conflict | Error code 101 |
Source: IRS Form SS-4, its instructions, and IRS EIN guidance, verified July 2026.
Four of the 12 decide whether an application succeeds: Form SS-4 with its 18 fields, line 7b, the responsible party on line 7a, and the CP-575 that confirms the result. The other 8 explain the vocabulary around them.
In what order do the EIN terms appear in an application?
The terms appear in 5 stages: the entity forms, Form SS-4 collects 18 fields, line 7b picks the channel, the IRS assigns the 9-digit EIN, and the CP-575 confirms it. A 147C replaces that letter years later.
| Stage | Terms in play | What happens | Cost |
|---|---|---|---|
| 1. Before filing | Responsible party, disregarded entity | The state approves the entity and 1 person takes control of it | $0 to the IRS |
| 2. The form | Form SS-4, third party designee | 18 numbered fields and 1 signature block get completed | $0 |
| 3. The channel | Line 7b, SSN, ITIN, TIN | An SSN or ITIN opens the 15-minute online route; Foreign opens the fax route | $0 |
| 4. The number | EIN, reference number 101 | The IRS assigns 9 digits, or returns a 101 name conflict and issues 0 | $0 |
| 5. The proof | CP-575, 147C letter | The IRS mails 1 confirmation letter; a 147C replaces it on request | $0 |
Source: IRS Form SS-4 instructions, verified July 2026.
Stage 3 is where the vocabulary stops being academic. An SSN or an ITIN on line 7b sends the applicant to the IRS online assistant, which runs Monday to Friday, 7 a.m. to 10 p.m. Eastern and returns the EIN inside 1 session of 15 minutes. The word Foreign on the same line sends the identical form to 1 of 2 fax numbers, where processing runs days to weeks with no tracking number and no status page.
Stage 4 produces a number that never changes. The 9 digits assigned in stage 4 stay with the entity for its full life, survive an address change, survive a change of responsible party reported on Form 8822-B within 60 days, and cost $0 in year 2 and every year after.
What is an EIN?
An EIN is the 9-digit Employer Identification Number the IRS assigns to a business entity for federal tax purposes. The IRS charges $0 for it, prints it as 2 digits, a hyphen, then 7 digits, and issues 1 per entity.
The 2 digits in front of the hyphen form the prefix. The prefix records which IRS campus or which application channel issued the number, and it carries no meaning for tax treatment. The 7 digits after the hyphen are the serial portion.
An EIN attaches to the entity, not to the owner. One person who forms 3 companies holds 3 EINs. One company that opens 5 bank accounts still holds 1 EIN. An EIN never renews and never expires, which puts the cost in year 2 at $0 and the cost in every year after at $0.
Source: IRS, Employer ID Numbers, verified July 2026.
What is Form SS-4?
Form SS-4 is the IRS application for an Employer Identification Number. It carries 18 numbered fields and 1 signature block. The IRS charges $0 for the form and $0 for the EIN the form produces.
Two fields decide most outcomes. Line 1 takes the legal entity name and has to match the state formation record character for character, because LLC and L.L.C. read as 2 different entities to the IRS. Line 7b takes the responsible party's tax ID and decides which filing channel accepts the form.
The remaining 16 fields cover the mailing address on lines 4a and 4b, the entity type on line 9a, the reason for applying on line 10, the start date on line 11, the fiscal year on line 12, and the employee counts on the 3 boxes of line 13. A blank line 13 causes rejection. Enter 0 in all 3 boxes when the entity hires nobody.
Source: IRS Form SS-4 and its instructions, verified July 2026.
What is a CP-575 letter?
A CP-575 is the official IRS notice that confirms a newly assigned EIN. It prints the 9-digit EIN, the legal entity name, and the mailing address. The IRS issues 1 CP-575 per EIN and never reprints it.
The CP-575 is the document banks and payment platforms verify against. Each platform sets that rule itself, not the IRS: Mercury, Wise, Relay, Stripe, PayPal, and Amazon each request the letter during business verification and match the name printed on it against the state formation document. A name mismatch created on line 1 of Form SS-4 surfaces here, months after filing.
Store a copy the day it arrives. The IRS replaces a lost CP-575 with a 147C letter, never with a second CP-575.
Source: IRS notice CP-575, verified July 2026. Platform verification rules are set by each platform, not the IRS.
What is a 147C letter?
A 147C letter is the IRS replacement confirmation for an EIN already assigned. The IRS issues it when the original CP-575 is lost. It carries the same 9-digit EIN and the same legal name, and costs $0.
Only the responsible party named on line 7a of the original Form SS-4, or a person that party authorizes, requests a 147C. The IRS verifies identity on the call before releasing the number. International applicants reach the IRS on 267-941-1099.
Banks accept a 147C in place of a CP-575. The 2 documents carry identical EIN and name data, and neither one costs anything.
Source: IRS, verified July 2026.
What is a responsible party on an EIN application?
The responsible party is the individual who controls the entity, its funds, and its assets. Line 7a of Form SS-4 takes that person's name. The IRS accepts 1 responsible party per EIN, and it has to be a person.
A parent company, a formation agent, or an accountant named on line 7a triggers rejection. The IRS wants a human being with control, which means a manager, a director, a general partner, or an LLC member.
The responsible party changes over the life of a company. The IRS requires Form 8822-B to report that change within 60 days. An EIN whose responsible party record is stale keeps working, and the IRS mails its notices to the wrong person.
Source: IRS Form SS-4 instructions and Form 8822-B, verified July 2026.
What is line 7b on Form SS-4?
Line 7b takes the responsible party's SSN, ITIN, or EIN. An applicant who holds none of the 3 enters the word Foreign. That single entry decides the route: Foreign blocks the IRS online tool and sends the form to fax.
Line 7b is the most consequential field on all 18. The IRS online assistant validates the entry against SSN and ITIN records in real time, so an applicant with neither number stops at that screen. The paper form has no such check.
Nothing about Foreign on line 7b weakens the EIN. The 9-digit number that arrives is identical to the number an SSN holder receives, and the CP-575 that confirms it is the same document. The IRS asks for no passport, no visa, and no identity upload with Form SS-4.
Source: IRS Form SS-4 instructions, verified July 2026.
What is a TIN?
A TIN is a Taxpayer Identification Number, the umbrella term for every 9-digit identifier the US tax system uses. The IRS lists 5 types: SSN, EIN, ITIN, ATIN, and PTIN. An EIN is 1 of the 5.
The Social Security Administration issues the SSN. The IRS issues the other 4. Every one of the 5 carries 9 digits, which is why forms asking for a TIN accept an EIN in the same box.
A business form asking for a TIN wants the EIN. A personal tax form asking for a TIN wants the SSN or the ITIN. The distinction matters on Form W-9 and Form W-8BEN-E, where the wrong number in the box sends the payer's reporting to the wrong tax account.
Source: IRS, Taxpayer Identification Numbers, verified July 2026.
What is an ITIN?
An ITIN is a 9-digit Individual Taxpayer Identification Number the IRS issues to a person who owes US tax filings and holds no SSN. Every ITIN begins with 9. A person applies on Form W-7, not on Form SS-4.
An ITIN belongs to a person. An EIN belongs to a company. The 2 numbers answer different questions, and an EIN application never requires an ITIN first. Line 7b accepts the word Foreign in place of both.
An ITIN that appears on no federal tax return for 3 consecutive years expires. An EIN never expires. That is the sharpest difference between the 2 numbers over time.
Source: IRS, Individual Taxpayer Identification Number, verified July 2026.
What is an SSN in the EIN application process?
An SSN is the 9-digit Social Security Number the Social Security Administration issues. On an EIN application it does 1 thing: an SSN on line 7b unlocks the IRS online assistant, which issues an EIN in 15 minutes for $0.
The IRS online assistant runs Monday to Friday, 7 a.m. to 10 p.m. Eastern. The session expires after 15 minutes of inactivity and restarts from the first screen. It validates line 7b against SSN and ITIN records before it will continue.
Have an SSN? irs.gov is free — really. Use the online assistant, finish in 15 minutes, and pay nobody. An EIN service earns its fee only where the online tool refuses the applicant.
Source: IRS EIN online assistant, verified July 2026.
What is a third party designee on Form SS-4?
A third party designee is the person an applicant authorizes to receive the EIN from the IRS and answer questions about Form SS-4. The authorization sits above the signature block. It ends the moment the IRS assigns the EIN.
The designee section takes a name, an address, a phone number, and a fax number. The applicant still signs the form. A designee never becomes the responsible party, and a designee never gains authority over the entity's tax account.
Because the authority terminates at assignment, a designee cannot file later returns, cannot change the address, and cannot request a 147C years afterwards. Those actions belong to the responsible party named on line 7a.
Source: IRS Form SS-4 instructions, verified July 2026.
What is a disregarded entity?
A disregarded entity is a single-member LLC the IRS looks through for federal income tax. Line 8b of Form SS-4 sets it: 1 member defaults to a disregarded entity, 2 or more members default to a partnership.
Disregarded status describes tax treatment, not legal existence. The LLC still holds its own EIN, its own bank account, and its own liability shield under state law.
A disregarded entity with a foreign owner files Form 5472 attached to a pro forma Form 1120 every year, even in a year with $0 of revenue. The IRS sets the penalty for failing to file Form 5472 at $25,000 per year, so the annual filing is not optional.
Source: IRS Form 5472 instructions and IRC section 6038A, verified July 2026.
What is EIN reference number 101?
Reference number 101 is the error the IRS online assistant returns when the entity name conflicts with an existing record. The tool stops the application at that screen and issues no EIN. The paper route resolves it.
The conflict comes from a name already registered in another state, from a name too close to an existing IRS record, or from the same responsible party applying more than once in 1 day. The IRS limits online issuance to 1 EIN per responsible party per day.
A 101 does not mean rejection of the business. It means a human at the IRS has to review the name. Filing Form SS-4 by fax puts the application in front of that human. Fax to 855-641-6935 for a US-based entity, or 855-215-1627 from outside the United States.
Source: IRS EIN online assistant messages, verified July 2026.
Which EIN terms matter when the applicant has no SSN?
Three terms matter: line 7b, which takes the word Foreign; the responsible party on line 7a, who has to be a person; and the fax route, on 855-641-6935 for US-based entities or 855-215-1627 for international applicants.
| Channel | Number | Who uses it |
|---|---|---|
| IRS fax, US-based entity | 855-641-6935 | The entity has a US business address |
| IRS fax, international | 855-215-1627 | The entity has no US business address |
| IRS international phone line | 267-941-1099 | International applicants calling the IRS directly |
Source: IRS, verified July 2026.
Two facts settle the rest. The IRS asks for no Social Security Number on line 7b, and the IRS asks for no identity document with Form SS-4. Line 7b carries 1 word, and the IRS accepts it.
See the vocabulary applied country by country on the ein by country (hub: 20 country H2 chunks) page, and read what lands in the mailbox afterwards on the ein confirmation letter page. The field-by-field rules sit on the SS4 form checklist.
What do the terms in this EIN glossary cost?
Nothing at the IRS. Form SS-4 costs $0, the EIN costs $0, the CP-575 costs $0, and a 147C replacement costs $0. Year 2 costs $0, because an EIN never renews. Filing services charge for execution, not for the number.
| Filed by | Price | Filing guarantee in writing | Year 2+ |
|---|---|---|---|
| Yourself, direct to the IRS | $0 | None | $0 |
| einnumber.co Standard | $67 | Filed by fax within 5 business days or the filing is free | $0 |
| einnumber.co Fast | $97 | Filed and the IRS call made within 24 hours, guaranteed — or the filing is free | $0 |
| Northwest | $200 | Not stated | $0 |
| ZenBusiness | $99 | Not stated | $0 |
| Rocket Lawyer | $59.99 | Not stated | $0 |
Competitor prices verified July 2026. Northwest reflects the no-SSN rate.
Read this before paying anyone, including us. An SSN on line 7b means the IRS issues the EIN at irs.gov in 15 minutes for $0. The $67 exists for the applicants the online tool blocks: a paper form, a fax line with no tracking, and 18 fields that have to be right the first time. Fast costs $97 and adds the IRS call within 24 hours.
Compare the full price breakdown on the how much does an EIN cost page, or get started now.