EIN Glossary of Terms: 33 Definitions (2026)

What is an EIN?

An EIN is the 9-digit federal tax identification number the IRS assigns to a business entity. It prints as 2 digits, a hyphen, then 7 digits. The IRS charges $0 to issue one.

One entity holds one EIN for its whole life. The number never expires, never renews, and costs $0 in year 2 and every year after. A company that changes its address, its name, or its owners keeps the same 9 digits.

The EIN identifies the entity to 3 audiences at once: the IRS on every return, the bank on every account application, and the payer on every Form 1099 or W-9. Those 3 audiences all check the same 9 digits against the same legal name.

What is a federal tax ID number?

A federal tax ID number is the same 9-digit EIN under a different name. Banks, payroll providers, and marketplaces use the 2 labels interchangeably, and no separate number exists behind the second label.

The synonym causes real applications to stall. An onboarding form that asks for a federal tax ID number and a second form that asks for an EIN want the identical 9 digits from the identical CP-575 letter.

State-issued numbers are the genuine exception. A state tax ID, a sales tax permit number, and a state employer account number are separate numbers issued by 1 of the 50 states, and none of them is an EIN.

What is an EIN prefix?

The EIN prefix is the first 2 digits of the 9-digit number, printed before the hyphen. It records which IRS campus assigned the EIN. The prefix carries no information about the business itself.

The prefix is the reason an EIN reads as 2 digits and 7 digits rather than 3 digits and 6. A number written without the hyphen stays valid, because the IRS stores 9 digits and the hyphen is formatting.

The prefix proves nothing about validity. A well-formed 9-digit string is not an assigned EIN, and the only proof of assignment is an IRS document: the CP-575 at issue, or the 147C letter afterwards.

What is a TIN?

A TIN is a taxpayer identification number, the IRS category that contains several number types. An EIN is 1 type of TIN. An SSN and an ITIN are 2 other types, both issued to individuals.

The relationship runs one way. Every EIN is a TIN, and most TINs are not EINs. A form that asks for a TIN accepts the EIN of an entity or the SSN of an individual, depending on who signs it.

The distinction decides which entry of Form W-9 gets filled. An entity enters its 9-digit EIN. An individual sole proprietor enters an SSN instead, and a business return filed under the wrong category triggers a matching notice.

The full comparison sits on the EIN vs TIN page.

What is an IRS name control?

A name control is the 4-character code the IRS derives from an entity's legal name and stores beside its EIN. Every electronic filing matches the EIN against those 4 characters before the return is accepted.

The name control explains rejections that look impossible. An EIN entered correctly still fails when the name on the filing produces different first 4 characters than the name the IRS recorded on Form SS-4.

Punctuation and articles change the result. The IRS builds the code from the legal name on the formation document, so a comma, an ampersand, or a dropped word shifts the 4 characters and breaks the match.

The character-by-character rules sit on the IRS name control page.

What is a DBA in EIN terms?

A DBA is a trade name a business operates under, and it holds no EIN of its own. The EIN belongs to the legal entity behind the name, and 1 entity runs any number of DBAs on 1 EIN.

Form SS-4 records the legal name on line 1 and the trade name on line 2, which is why both appear on the CP-575. The IRS matches filings to line 1, and the name control comes from line 1.

Banks read the pair the same way. An account opened under a trade name still lists the legal entity as the accountholder, and the CP-575 has to show the trade name on line 2 for the bank to connect them.

What is Form SS-4?

Form SS-4 is the IRS application for an EIN. It is 1 page, it costs $0 to file, and it collects the legal name, the entity type, the reason for applying, and the responsible party.

Every EIN route runs on the same form. The online assistant, the fax route, and the mail route all collect the Form SS-4 fields, and the form itself is what an IRS reviewer reads when the online tool stops.

Two lines decide most outcomes. Line 1 sets the legal name and the name control derived from it. Line 7b sets the responsible party's identifying number, and it accepts the entry Foreign when that person holds no SSN.

What is a CP-575?

The CP-575 is the IRS notice that confirms a new EIN. The IRS issues 1 CP-575 per EIN and never reprints it. It prints the 9 digits beside the legal name the number was assigned to.

The single-issue rule is what makes the document valuable. A bank asking for proof of an EIN is asking for the pairing of the number and the name, and the CP-575 is the record of that pairing at assignment.

It is one of the 2 deliverables we hand over at $99: the 9-digit EIN and the official IRS CP-575 letter. A CP-575 that is lost is replaced by a 147C letter, never by a second CP-575.

What is a 147C letter?

A 147C letter is the IRS replacement for a lost EIN confirmation. It restates the same 9-digit EIN and the legal name on file. The IRS charges $0 and releases it to an authorized person only.

The 147C exists because the CP-575 prints once. After that single printing, the 147C is the only document that carries IRS authority for the number, and banks accept it in place of the original notice.

The request is an identity check before it is a paperwork step. The IRS verifies that the caller holds authority over the entity, which is why the request cannot be delegated to someone with no recorded role.

The request script and what the IRS asks for are on the 147C letter page, and the anatomy of the original notice is on the CP-575 page.

What is an EIN confirmation letter?

An EIN confirmation letter is the umbrella term for the 2 IRS documents that prove an EIN: the CP-575 issued once at assignment, and the 147C letter issued afterwards. Both carry the same 9 digits.

The umbrella term is why 2 people describing the same request mean different documents. A bank asking for an EIN confirmation letter accepts either one, because both come from IRS records rather than from the business.

No third document qualifies. A screenshot, an accountant's letter, and a filed return each show the number without proving the IRS assigned it, and an account opening that requires proof rejects all 3.

What the document contains, line by line, is on the EIN confirmation letter page, and what reviewers check is on the what banks and platforms verify page.

What is Form W-9 in EIN terms?

Form W-9 is the request a payer sends before paying a business. Line 1 carries the legal name and Part I carries the 9-digit EIN. The signature in Part II attests that both entries are correct.

The W-9 is the only route to a private company's EIN. No public database lists it, so a payer, a client, or a marketplace obtains the number by asking the entity to sign the form.

The name on line 1 has to be the legal name, not the trade name. A W-9 that pairs an EIN with a DBA produces a name control mismatch when the payer files the matching Form 1099 later.

Where does an EIN appear on Form W-2?

Box b of Form W-2 carries the employer's 9-digit EIN. Every W-2 a business issues prints the same number, and each employee holds a copy of it for the tax year it covers.

The W-2 is the widest surviving copy of an EIN. A business with 20 employees distributed 20 copies of its EIN for that year, which is why payroll records recover a lost number faster than an IRS request.

An employer EIN and a company EIN are 1 number, not 2. A business does not hold a separate payroll identifier, and the number in box b is the same number on the CP-575.

What is Form 8822-B?

Form 8822-B is the IRS form that updates a business address or the responsible party recorded against an EIN. It costs $0. The EIN itself never changes, because the form updates records rather than reassigning a number.

The IRS instructions for Form 8822-B require notice within 60 days of a responsible party change. The form is how the record stays current, and a stale responsible party is a common cause of a refused 147C request years later.

A legal name change runs on a different track. Form 8822-B handles the address and the responsible party, and the entity keeps its original 9-digit EIN through every one of those updates.

The form is walked line by line on the Form 8822-B page.

What is Form 5472?

Form 5472 reports transactions between a US entity and its foreign related parties. A foreign-owned single-member LLC files it with a pro forma Form 1120, and the filing requires an EIN before it can be made.

The form is the reason an EIN is not optional for a foreign-owned LLC with no US income. The obligation attaches to the entity, and the return cannot be filed without the 9-digit number identifying it.

The IRS instructions for Form 5472 set the penalty for a failure to file at $25,000 per form per tax year. That figure is the practical case for obtaining the EIN before the first reportable transaction rather than after.

Who is the responsible party on an EIN application?

The responsible party is the 1 individual who controls the entity and its funds. Form SS-4 names exactly 1 person on line 7a. The IRS requires a natural person, not a company.

Control is the test, not title or ownership percentage. A company with 4 owners still names 1 responsible party, and the person named is the one who directs how the entity's funds and assets are used.

The role outlives the application. The IRS releases EIN information to the responsible party, so the person on file is the person who can request a 147C letter. Form 8822-B updates the name when it changes.

Read the full test, the update procedure, and the IRS deadline on the responsible party ein page.

What is a third party designee?

A third party designee is the person the applicant authorizes on Form SS-4 to receive the EIN and answer IRS questions about the application. The authority ends when the EIN is assigned.

The designee block sits at the bottom of Form SS-4 and carries its own name, address, phone, and fax. It is how a filing service receives the number directly rather than waiting on the mail.

The authority is narrow and short. It covers the assignment of that 1 EIN and nothing after it, which is why a designee cannot request a 147C letter later and the responsible party can.

What is an authorized person in EIN terms?

An authorized person is someone the IRS will release EIN information to: the responsible party, an owner, a partner, a corporate officer, or a holder of a filed power of attorney. The IRS verifies that authority first.

The definition is the gatekeeper on every recovery route. A 147C request from a bookkeeper with no recorded role fails at the verification step, however accurate the entity details in the request are.

Two documents create authority where records are silent. Form 8822-B updates the responsible party on file, and Form 2848 records a power of attorney. Both close the gap before a recovery request, not during it.

What is an SSN in EIN terms?

An SSN is the 9-digit Social Security Number issued to an individual. It is a personal identifier, never an entity identifier. An EIN application accepts an SSN on line 7b, and does not require one.

The SSN decides the route rather than the outcome. A responsible party with an SSN uses the IRS online assistant, whose session the IRS caps at 15 minutes, and receives the EIN at $0. Everyone else uses the fax route.

The 2 numbers look identical and behave differently. Both hold 9 digits, and only the EIN belongs to a business. A business return filed under an SSN reports the individual, which is what a name control mismatch reveals.

Which number a business reports under is settled on the EIN vs SSN page.

What is an ITIN?

An ITIN is a 9-digit individual taxpayer identification number the IRS issues to a person who has a US tax filing obligation and no SSN. It is a personal number, and it is not required for an EIN.

The sequence confuses applicants because both numbers hold 9 digits and both come from the IRS. An EIN identifies an entity and an ITIN identifies a person, and the EIN application runs without one.

Waiting for an ITIN before applying for an EIN adds delay and changes nothing. Form SS-4 line 7b accepts the entry Foreign, which is the field the IRS designed for a responsible party with neither number.

The two numbers are separated on the EIN vs ITIN page.

What does line 7b mean on Form SS-4?

Line 7b is the field on Form SS-4 for the responsible party's SSN, ITIN, or EIN. It accepts the entry Foreign when that person holds none of the 3, and the IRS assigns the EIN anyway.

Line 7b is the single most consequential field on the form for a non-resident. The word Foreign is the IRS instruction for that case, and the application moves from the online assistant to the fax route.

No identity document accompanies the entry. Form SS-4 asks for no passport, no scan, and no upload, and the IRS assigns the number on the strength of the form. The IRS fee stays $0 on that route.

The complete no-SSN chapter sits on the EIN without SSN page.

What is the IRS EIN online assistant?

The EIN online assistant is the IRS web tool that issues an EIN at $0. The IRS sets its session limit at 15 minutes. It requires a responsible party with an SSN or ITIN, and runs during published IRS hours.

The tool is the fastest route and the narrowest. It ends the session on any condition it cannot resolve automatically, returning a reference number rather than an EIN, and it holds no partial applications.

Anyone with an SSN belongs here. The tool is free, it finishes inside the IRS 15-minute session, and paying a service for that route buys nothing. The fax route exists for the applications the tool declines to complete.

All 4 application routes are compared on the how to apply for an EIN page.

What is the EIN fax route?

The fax route sends a completed Form SS-4 to an IRS reviewer instead of the online tool. The IRS fax numbers are 855-641-6935 for entities based in a US state and 855-215-1627 for international applicants.

A human reviewer is the point of the route. Every condition the online assistant refuses to resolve automatically, including line 7b marked Foreign and a name that resembles an existing one, reaches a person on this route.

The 2 fax numbers are not interchangeable. The number is chosen by where the entity is based, and a Form SS-4 sent to the wrong line restarts the wait rather than shortening it. The IRS fee stays $0.

What is the IRS international line for EIN questions?

The IRS international line for EIN matters is 267-941-1099. It handles applicants and entities outside the United States, including 147C requests where the authorized person is reached abroad.

The line is not toll-free and it is not the domestic business line. Calling from outside the US is the case it was built for, and the caller is verified as an authorized person before information is released.

Preparation shortens the call. The legal name exactly as filed, the address on record, and the responsible party on file are the 3 items checked, and a mismatch on any 1 ends the call without a number.

What is a business day in EIN terms?

A business day is Monday to Friday, excluding US federal holidays. Every IRS processing window and every written delivery commitment counts in business days, so a weekend adds calendar time and no processing time.

The definition is the difference between 7 business days and 7 calendar days. A filing that starts on a Thursday spans 2 weekends before the seventh business day, which is 11 calendar days on the wall.

Our guarantee uses this definition without exception: delivered within 7 business days of filing or the $99 is refunded automatically, and we file within 1 business day of receiving your completed details.

The method-by-method timeline is on the how long does it take to get an EIN page, and you can model a date with the ein processing time estimator (tool).

What is EIN reference number 101?

Reference number 101 is a name conflict. The IRS online assistant found an entity name resembling one already in its records, across all 50 states, and ended the session before assigning an EIN.

The code is not a rejection of the application. The same Form SS-4 reaches an IRS reviewer on the fax route, where a person compares the names that the automated check refused to separate.

Reapplying online returns 101 again, because the comparison runs identically each session. Repeated attempts add reference number 105, which closes the tool for the day. The IRS fee stays $0 on every attempt.

What are EIN reference numbers 102 to 115?

Reference numbers 102 to 115 are the 12 remaining codes the IRS online assistant returns when it stops. They cover identity mismatches, existing EIN conflicts, daily limits, and system conditions. All 13 codes route to fax.

The codes split into 3 groups. Data conditions cover 101 through 107, system conditions cover 109 through 113, and limit conditions cover 114 and 115. Only the first group involves anything the applicant entered.

Reference 114 is the daily limit: the IRS issues 1 EIN per responsible party per day. Reference 102 is an SSN or ITIN mismatch, and line 7b marked Foreign avoids that check entirely.

All 13 codes, with the cause and the route for each, are on the EIN reference number 101 page.

What is a disregarded entity?

A disregarded entity is a single-owner business the IRS looks through for income tax, reporting its activity on the owner's return. It still holds its own EIN, because the EIN identifies the entity rather than the taxpayer.

The default applies to a single-member LLC unless an election changes it. The LLC exists in state law and disappears in federal income tax, which is why 1 business generates 2 different answers to who files.

Disregarded status does not remove filing obligations. Employment tax and excise tax are filed under the entity's own EIN, and a foreign-owned single-member LLC files Form 5472 with a pro forma Form 1120.

What is a single-member LLC in EIN terms?

A single-member LLC is an LLC with 1 owner. It obtains its own 9-digit EIN, and it is treated as a disregarded entity for income tax by default. Banks require the EIN before opening an account.

Adding a second member changes the federal classification to a partnership, and that change requires a new EIN. The state entity survives the change, and the federal number does not.

The EIN is the practical requirement long before any return is due. An account application, a payment processor, and a marketplace each check the 9 digits against the legal name on the CP-575.

The LLC chapter, including classification and reporting, is on the EIN for LLC page.

What is a sole proprietorship in EIN terms?

A sole proprietorship is an unincorporated business with 1 owner and no separate legal entity. It reports on the owner's SSN unless it hires employees, and it obtains an EIN at $0 in every case.

It is the 1 structure where an EIN is genuinely optional at the start. Employees, certain excise taxes, and a bank that requires an entity number are the conditions that make it required.

Incorporating later does not carry the number across. A sole proprietorship that becomes a corporation or a partnership needs a new EIN for the new entity, and the old number stays with the old structure.

What is a new EIN trigger?

A new EIN trigger is a change that creates a different entity in federal tax terms. Incorporating a sole proprietorship, adding a second LLC member, and forming a new company each require a new 9-digit EIN.

The rule tracks entity identity, not business activity. A name change, an address change, a new location, and a new owner of the same entity all keep the original EIN, and Form 8822-B records the address.

The distinction decides whether a lookup or an application is the right move. Recovering a number helps when the entity survived, and an entity that did not survive the change needs a fresh application.

The full change matrix is on the when do you need a new EIN page.

What is SEC EDGAR in EIN terms?

SEC EDGAR is the Securities and Exchange Commission filing system. It publishes the EIN of public companies in the header of filings such as the 10-K and 10-Q. Access costs $0.

EDGAR covers public companies because federal securities law requires the filings. It covers no private company, so a search that returns nothing about a private business has produced the correct result.

A signed Form W-9 is the route for the companies EDGAR omits, and Part I of that form carries the 9 digits. No IRS tool searches private EINs by company name.

Every legitimate search route is listed on the EIN number lookup page, and recovery of your own number is on the lost EIN number page.

What is the IRS Tax Exempt Organization Search?

The Tax Exempt Organization Search is the IRS tool that publishes the EIN of every registered tax-exempt organization. Form 990 prints the same EIN on page 1. Both sources cost $0.

Nonprofit EINs are the most openly available category, because tax-exempt organizations file Form 990 annually and the IRS publishes those returns. A donor reaches the number without contacting the organization.

Match the EIN to the legal entity rather than the brand. A national body and a local chapter hold separate EINs, and the search lists each under its own legal name.

What is a TIN mismatch?

A TIN mismatch is an IRS notice that an EIN and a name on an information return do not match its records. The comparison runs against the 4-character name control stored beside the EIN.

The notice reaches the payer who filed the Form 1099, and the payer then asks the business for a corrected Form W-9. The 9 digits are correct in most cases, and the name is what fails.

Three causes account for the bulk of them: a trade name entered where the legal name belongs, a legal name changed without an IRS record of it, and an abbreviation that shifts the first 4 characters.

Confirmation steps for a counterparty number are on the verify EIN number page.