EIN vs SSN vs ITIN: US Taxpayer ID Numbers Compared

The United States runs on nine-digit taxpayer numbers, and three of them dominate every form you will ever see: the SSN, the EIN and the ITIN. They are the same length, they all show up in the same database columns, and they are constantly confused with each other — by form designers, by validation code, and by test data that puts the wrong shape in the wrong field. This guide compares who issues each number, who needs it, what the digits mean, and how to tell them apart from format alone.

One umbrella: taxpayer identification numbers

The IRS groups all of these under one term: TIN, or taxpayer identification number — any number the agency accepts as identifying a taxpayer on a return or statement ^[irs-tin]. Two of the five TIN types cover almost everyone: the SSN for individuals and the EIN for entities. The ITIN fills the main gap — individuals who must file US taxes but cannot get an SSN — while two narrower types cover pending adoptions (ATIN) and paid tax preparers (PTIN).

SSN: the personal number everything else leans on

The Social Security number is the oldest and most consequential of the three — created in 1936 for tracking earnings, and long since turned into a de facto national identifier for credit, banking and employment. It is written XXX-XX-XXXX: historically an area number tied to the issuing state, a two-digit group number, and a four-digit serial. That geography is gone: since June 25, 2011 the SSA assigns SSNs by randomization, drawing from previously unassigned ranges and eliminating any meaning in the first three digits ^{[ssa-randomization]}.

Structure still rules out plenty of values. A valid SSN never has an area of 000 or 666, a group of 00, or a serial of 0000 — and crucially for this comparison, the SSA never issues areas 900–999. That reserved 9XX space is exactly where ITINs live, and it is also why a well-built SSN generator and validator can emit masked, never-issuable placeholders that cannot collide with a real person. The full digit-by-digit story is in our US SSN format guide.

EIN: the same nine digits, regrouped for entities

An employer identification number is the business world's SSN — required to hire employees, open business bank accounts, file entity returns, and issue 1099s. It is free, issued directly by the IRS in minutes online ^[irs-ein], and formatted XX-XXXXXXX: a two-digit prefix, a hyphen, then seven digits. That 2+7 grouping is the fastest visual tell that a number is an EIN rather than an SSN or ITIN.

The prefix once encoded which IRS campus assigned the number. Campus assignment ended as a geographic signal in 2001, and applications now flow mostly through the online system, which draws from its own prefix pool — but the IRS still publishes the full table of valid prefixes per assignment channel, which validators can use to reject impossible EINs ^{[irs-ein-prefixes]}.

ITIN: for taxpayers outside the SSN system

The individual taxpayer identification number exists for one purpose: letting people who are not eligible for an SSN — nonresident aliens with US filing obligations, their spouses and dependents, certain visa holders — file and pay federal taxes ^[irs-itin]. It borrows the SSN's 3+2+4 shape (9XX-XX-XXXX) but is instantly recognizable: an ITIN always begins with 9, and its fourth and fifth digits fall within the ranges 50–65, 70–88, 90–92 or 94–99 ^[irs-itin].

Two properties set ITINs apart from the other two numbers. First, they confer nothing beyond tax processing — no work authorization, no Social Security credits, no immigration status. Second, they lapse: an ITIN unused on a federal return for three consecutive tax years expires and must be renewed with Form W-7 ^[irs-itin]. If the holder later becomes eligible for an SSN, the SSN takes over and the ITIN is retired.

Side by side: the three numbers compared

Telling them apart at a glance

Given a bare nine-digit number on a form or in a database, three checks identify it the way a format validator would:

1. Check the grouping. 2+7 with the hyphen after the second digit is an EIN. 3+2+4 means a personal number — continue.
2. Check the first digit. A 9 up front means it cannot be a real SSN; it is ITIN-shaped (or a deliberately fake placeholder).
3. Check the ITIN middle pair. Fourth and fifth digits in 50–65, 70–88, 90–92 or 94–99 confirm the ITIN pattern ^[irs-itin]; outside those ranges, the number is not a valid ITIN either.

That principle — format-valid but guaranteed-fictional — is the same one behind reserved 555 phone numbers and sandbox credit card ranges. If you need full test profiles around these numbers, the fake identity generator produces internally consistent people, and the PII in test environments guide covers the compliance reasoning. For how other countries structure their equivalents of the SSN, see national ID number formats explained.

The bottom line

SSN, EIN and ITIN are three answers to one question — who is this taxpayer? — split by what kind of taxpayer it is. The SSA numbers people; the IRS numbers entities and the people the SSA cannot. Their formats were designed to coexist: the 2+7 grouping walls EINs off visually, and the reserved 9XX space keeps ITINs from ever colliding with an SSN. Learn those two facts and you can classify any US taxpayer number — real or test data — at a glance.