Taxpayer Identification Number: Types and Who Uses Each

Q: What is a taxpayer identification number?

A taxpayer identification number is the umbrella term for the identifying numbers the IRS uses to administer tax law. It is a category rather than a single number, and five identifiers belong to it: the Social Security number, the employer identification number, the individual taxpayer identification number, the adoption taxpayer identification number, and the preparer tax identification number. All five are nine digits. The Social Security Administration issues one of them and the IRS issues the other four. When a form asks for a taxpayer identification number, it is asking which of these applies to the party signing it, which is why the same box gets filled in differently by an individual and by a company.

Q: Is a taxpayer identification number the same as an EIN?

No. An employer identification number is one type of taxpayer identification number, not another name for the category. The distinction matters on payee forms, because a business entity is expected to give its employer identification number while an individual is expected to give a Social Security number. Reading the two phrases as synonyms is the single most common cause of a mismatched name and number pair, and the mismatch does not surface at the moment it is made. It surfaces months later, when the IRS compares what you filed against its own records and sends a notice about the returns that failed to match.

Q: What are the five types of taxpayer identification numbers?

The five are the Social Security number issued by the Social Security Administration on Form SS-5, the employer identification number issued by the IRS on Form SS-4, the individual taxpayer identification number issued by the IRS on Form W-7, the adoption taxpayer identification number issued by the IRS on Form W-7A, and the preparer tax identification number issued by the IRS on Form W-12. A small employer realistically encounters three of them: the Social Security number of an employee, the employer identification number of an incorporated vendor, and the personal number of a contractor who never formed an entity. Adoption and preparer numbers exist outside the payroll relationship entirely.

Q: Which taxpayer identification number do I collect from a contractor?

Whichever one the contractor certifies on Form W-9, which depends on how they are organized rather than on what you would prefer. A sole proprietor gives a Social Security number, or an employer identification number if they obtained one. A partnership or a corporation gives its employer identification number. A single-member limited liability company that is disregarded for tax purposes reports under the owner rather than under the company. Your job is not to decide which is correct but to collect the signed form before the first payment, keep it, and check that the name and number pair matches IRS records before you file anything that carries it.

Q: Can an employee work using an ITIN?

No. An individual taxpayer identification number exists for federal tax reporting only. It does not authorize employment in the United States and it does not confer eligibility for Social Security benefits. IRS guidance for employers is direct on the point: do not accept one in place of a Social Security number for employee identification or for work. Employment authorization is established through Form I-9 and its acceptable documents, not through a tax number. If somebody who holds an individual number later becomes authorized to work, they apply to the Social Security Administration for a Social Security number, and wage reporting then runs under that number instead.

Q: How do I check that a name and taxpayer identification number match?

Two free government services cover the two populations. The IRS on-line matching program is for payers of reportable payments: it takes up to 25 name and number combinations on screen with immediate results, or up to 100,000 in a file with results inside 24 hours. For employees, the Social Security Administration offers a verification service for wage reporting, taking 10 names on screen for immediate results or up to 250,000 by file upload. The employee service is limited to wage reporting and is not a pre-employment screening tool, so a result from it is never a basis for an adverse decision about a worker.

Q: What happens if a 1099 has a missing or wrong taxpayer identification number?

It is treated as an incorrect information return, and the penalty depends on how quickly you fix it. For returns required to be filed in 2026 the IRS charges $60 per return when corrected within 30 days, $130 when corrected by August 1, and $340 after that or if it is never corrected, rising to $680 where the failure is due to intentional disregard. A mismatch also triggers a CP2100 or CP2100A notice, which starts a sequence of payee notices and can require backup withholding at 24 percent on future payments to that payee until a correct certification arrives.

A taxpayer identification number is any of five IRS identifiers. Which one you collect from employees and contractors, and how to check it before filing.

Nick Anisimov

FirstHR Founder

Payroll•

August 18, 2026

•

12 min

Taxpayer Identification Number

The phrase on every payee form is a category rather than a number, and five different identifiers sit inside it: which one you collect from an employee, which one you collect from a contractor, what to do when a new hire hands you one that cannot be used for wages, and how to check the pair before it reaches a filing

The first contractor I ever paid sent back a form with a Social Security number written in the box. The box was labeled taxpayer identification number, and I spent an evening convinced I had asked for the wrong thing and would have to ask again.

I had not. That evening was the cost of not knowing something small: taxpayer identification number is not a number at all. It is a category, five identifiers belong to it, and every payee form asks for the category while quietly expecting one specific member of it.

What follows is the employer view of that family. Which member you collect from whom, what to do when somebody hands you one that cannot be used for wages, how to check a name and number pair before it reaches a filing, and what the errors cost. I build the people and records tooling for companies without an HR department at FirstHR, which is an onboarding and HR platform rather than a payroll provider. This is general information, not tax advice.

TL;DR

A taxpayer identification number is the umbrella term for five IRS identifiers: the Social Security number, the employer identification number, the individual taxpayer identification number, the adoption number, and the preparer number. Employers collect a Social Security number from employees and either a Social Security number or an employer identification number from contractors. An uncorrected wrong pair costs $340 per return.

What the Phrase Actually Means

A taxpayer identification number is an identifying number used in administering federal tax law, and it is a category rather than one number. Five identifiers sit inside it, all nine digits long, issued by either the IRS or the Social Security Administration (Internal Revenue Service).

Definition

Taxpayer identification number (TIN)

The umbrella term for the nine-digit numbers the IRS uses to identify a taxpayer on a return, a payment, or an information return. It covers the Social Security number, the employer identification number, the individual taxpayer identification number, the adoption taxpayer identification number, and the preparer tax identification number. It is not a number you can apply for, because there is no application for the category itself, only for its members.

This is why the phrase feels slippery in practice. A bank, a payment platform, and a payee form all use it, and each of them means a different specific number depending on who is answering. The category is the question. The member is the answer.

Internal employee numbers are a separate matter with no tax meaning at all. The identifiers a business assigns for its own records are an administrative convenience, and they never go in a box asking for a taxpayer identification number.

The Five Types and Who Issues Them

Four of the five are issued by the IRS and one by the Social Security Administration, each on its own application form. Knowing which agency owns which number tells you where a replacement or a correction has to come from, which is the part that matters when something is wrong.

SSN, Social Security number

Issued by: Social Security Administration, on Form SS-5Belongs to: An individualThe number an employee gives you and the number that goes on their W-2. A sole proprietor without a business number also uses it on a W-9.

EIN, employer identification number

Issued by: IRS, on Form SS-4Belongs to: A business, estate, trust, or other entityThe number your own business files payroll returns under, and the number an incorporated contractor gives you instead of a personal one.

ITIN, individual taxpayer identification number

Issued by: IRS, on Form W-7Belongs to: An individual who must file but cannot get a Social Security numberNine digits beginning with a 9. It exists for federal tax reporting and nothing else. It does not authorize work and cannot be used for wage reporting.

ATIN, adoption taxpayer identification number

Issued by: IRS, on Form W-7ABelongs to: A child in a pending domestic adoptionTemporary, and issued so adoptive parents can claim the child while the Social Security number is still pending. An employer will never collect one.

PTIN, preparer tax identification number

Issued by: IRS, on Form W-12Belongs to: A paid tax return preparerIt identifies the person who prepared a return for compensation. It appears on your filings if you use an accountant, and never on a payee form.

Only three of the five ever reach a small employer: the Social Security number of an employee, the business number of an entity you pay, and the personal number of a contractor who never incorporated.

The one people underestimate is the individual number. It looks like a Social Security number, it is formatted like one, and it begins with a 9. It also cannot do the thing an employer most often needs a number to do, which is carry wages on a W-2.

Which Number You Collect From Whom

The number you collect depends on how the other party is organized, not on which relationship you are in. An employee always gives a Social Security number. A payee gives whichever identifier matches the entity that legally earned the money.

Who you are paying	Number they give you	Where you collect it
An employee	Social Security number	Form W-4 at hire, with the name exactly as it appears on the Social Security card
A sole proprietor contractor	Their Social Security number, or an employer identification number if they have one	Form W-9, before the first payment
A single-member LLC that is disregarded	The owner’s number rather than the company’s	Form W-9, where line 1 carries the owner’s legal name
A partnership or a corporation	The entity’s employer identification number	Form W-9, signed by somebody authorized for the entity
An LLC that elected corporate treatment	The company’s employer identification number	Form W-9, with the tax classification box completed
A foreign person or foreign entity	Not a domestic number at all	The W-8 series rather than a W-9

The collection form is doing more than gathering digits. Form W-9 is a signed certification of the name and number pair, and the signature is what makes it a defense when the pair later turns out to be wrong.

Getting the answer right also depends on getting the relationship right first. If somebody who should be an employee is being paid as a contractor, no amount of correct paperwork fixes it, and worker misclassification carries consequences that dwarf a reporting penalty.

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The Number Your Business Gives Out

When your business is the payee rather than the payer, the number you provide is your employer identification number if you are an entity, and your own Social Security number if you are a sole proprietor who never obtained one. Both are valid answers to the same question.

Plenty of sole proprietors get a business number anyway, for a reason that has nothing to do with tax law. It keeps a personal Social Security number off every form handed to a client. The employer identification number itself is free, and that page covers the application, the daily issuance limit, and how to replace a confirmation letter you cannot find.

The number your business files under also appears on every W-2 you issue and every information return you file, which is why it belongs in your permanent payroll records rather than in somebody’s memory.

When a New Hire Presents an ITIN

You cannot use it for employment. IRS guidance to employers states the position without qualification: do not accept an individual taxpayer identification number in place of a Social Security number for employee identification or for work (Internal Revenue Service).

The reason sits in what the number is for. The IRS issues it for federal tax purposes only, to people who have a filing obligation but are not eligible for a Social Security number. It does not authorize legal work in the United States and it does not qualify anybody for Social Security benefits or the earned income credit.

A tax number is not work authorization

Employment eligibility is established through the I-9 process and the documents that process accepts, never through a tax identifier. Presenting an individual taxpayer identification number says nothing about whether somebody may legally work, and treating it as if it did creates exposure on both sides at once.

The practical route is to keep the two questions apart. Work authorization is settled by I-9 documentation, on its own timeline, using the list of acceptable documents. Wage reporting is settled by a Social Security number, which somebody who becomes work authorized obtains from the Social Security Administration.

These numbers also expire. An individual number that is not used on a federal return for three consecutive years lapses at the end of that third year and has to be renewed on Form W-7 before it can be used again. The holder gets no reminder, so the discovery usually happens during a filing.

What worked for me

I keep the tax number and the work authorization document on separate steps of the same onboarding flow, with different owners. When they sat on one screen, people filled one in from the other, and every correction after that was a conversation nobody wanted to have. Splitting them cost one extra click and removed the whole category of mistake.

Checking the Pair Before You File

Two free federal services exist for this, one per population, and neither is widely used by small employers. The IRS on-line matching program covers payees, taking up to 25 name and number combinations on screen with immediate results, or up to 100,000 in a single file with results inside 24 hours (Internal Revenue Service).

For employees, the Social Security Administration runs a verification service that checks names and numbers against its own records: 10 at a time on screen for immediate results, or up to 250,000 by file upload with results the next government business day. It is limited to wage reporting.

Collect before the first payment

Ask for the signed certification form as part of setup, not as part of year-end. The request is routine before money moves and awkward afterwards, and the response rate difference is not small.

Check the name against the source document

Match the legal name to the Social Security card for an employee and to the certification form for a payee. A trading name in the legal name field is the mismatch that survives every visual check.

Run the pair through the right service

Payees go through the IRS matching program, employees through the Social Security Administration service. Enrollment for the IRS program requires an account and payer status, so do it before the week you need it.

Resolve mismatches in writing

Go back to the person with a specific request: confirm the legal name and the number as they appear on the card or the IRS letter. Keep the reply. It becomes your record of a reasonable attempt.

Re-check before the annual filing run

Names change, entities restructure, and individual numbers expire. A second pass in the weeks before filing catches the drift that a single check at hire never could.

One limit is worth stating plainly. The employee service exists to make wage reporting accurate, and a result from it is not evidence about immigration status or a basis for an adverse decision about a worker. Using it that way creates legal exposure of its own.

Building the check into your year-end payroll sequence is what makes it happen. As a standalone task that somebody remembers to do, it does not survive a busy quarter.

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What a Missing or Wrong Number Costs

A missing or incorrect number makes an information return incorrect, and the penalty is per return on a sliding scale set by how fast you fix it. For returns required to be filed in 2026, the IRS charges $60 within 30 days, $130 by August 1, $340 after that, and $680 where the failure is intentional.

When it is corrected	Penalty per return	What this looks like in practice
Within 30 days of the due date	$60	You caught it yourself, filed a correction, and the cost is an annoyance
After 30 days, by August 1	$130	A mismatch notice arrived and you acted on it in the same season
After August 1, or never	$340	The return stayed wrong through the cycle, which is the common small business outcome
Intentional disregard	$680	No maximum applies, and the amount is a floor rather than a ceiling

The number that should drive the process

$340 per return is the penalty for an information return with a missing or incorrect taxpayer identification number that is not corrected by August 1 of the filing year, for returns required to be filed in 2026. Thirty contractors with unchecked numbers is a five-figure exposure created by a step that takes an afternoon (IRS, information return penalties).

The penalty is not the whole cost. When filings contain pairs that do not match its records, the IRS sends a CP2100 or CP2100A notice, which starts a clock: you have 15 business days to send the payee a notice of your own, and an unanswered request eventually forces backup withholding at 24 percent on that payee.

That withholding sequence is a subject of its own, and the certification form article covers the notices, the deadlines, and how the withholding switches on and off. The point here is that it begins with an unchecked pair.

The reporting threshold has changed the arithmetic. For payments made on or after January 1, 2026, the nonemployee compensation threshold rose from $600 to $2,000 under the One Big Beautiful Bill Act, so fewer small payees generate a return, and the ones that do tend to be the relationships worth getting right. The two contractor information returns are still filed separately and on separate schedules.

Where Small Employers Get This Wrong

Almost every failure I have seen traces back to timing rather than to knowledge. The number is collected late, checked never, and stored somewhere that is not a system of record. The pattern repeats across companies that have nothing else in common.

Treating the category as a synonym for the business numberA form asking for a taxpayer identification number is asking which member of the family applies to the party signing it. An individual answering with a business number, or an entity answering with a personal one, produces a pair that will not match IRS records.

Accepting a name that does not match the numberThe check is on the pair, not the number alone. A contractor who trades under a brand name but registered the number under a personal legal name is the most common mismatch, and it passes every visual inspection you can do.

Collecting the number after the work is finishedOnce the invoice is paid, the leverage to ask is gone. The number is easy to get before the first payment and surprisingly hard to get in January, when the person has moved on and has no reason to reply.

Storing the number in an email threadA nine-digit identifier sitting in an inbox is a data problem waiting to happen. It belongs in the record system that holds the rest of the payee file, with access limited to the people who actually process payments.

Assuming a number that worked once still worksAn individual number that goes unused on a federal return for three consecutive years expires. A business that restructures may be issued a new number. Neither event sends you a notice, so both surface at filing time.

Four of these five are solved by one habit: collect the number before the first payment and check the pair the same week.

The fix is unglamorous. Make the number part of the intake step for both employees and payees, check the pair while the person is still responsive, and keep it with the rest of the file. Onboarding paperwork that collects it as a matter of course removes the annual scramble entirely.

It also helps to know which relationship you are actually in before the paperwork starts. The contractor relationship and the employment relationship collect different numbers on different forms, and sorting that out afterwards is far more expensive than sorting it out first.

Key Takeaways

Taxpayer identification number is a category covering five nine-digit identifiers, not a single number you can apply for.

Employees give a Social Security number; payees give whichever identifier matches the entity that earned the money, certified on a signed form.

An individual taxpayer identification number exists for federal tax reporting only and can never carry wages or establish work authorization.

Two free federal services check name and number pairs, one for payees through the IRS and one for employees through the Social Security Administration.

An uncorrected missing or wrong number costs $340 per return for filings required in 2026, and can trigger backup withholding at 24 percent.

Collect the number before the first payment and check the pair the same week, because both get harder once the relationship has ended.

Frequently Asked Questions

What is a taxpayer identification number?

It is the umbrella term for the identifying numbers the IRS uses to administer tax law, and it is a category rather than a single number. Five identifiers belong to it, all nine digits: the Social Security number, the employer identification number, the individual taxpayer identification number, the adoption taxpayer identification number, and the preparer tax identification number.

Is a taxpayer identification number the same as an EIN?

No. An employer identification number is one member of the category, not another name for it. An entity gives that number, an individual gives a Social Security number, and reading the two phrases as interchangeable is the most common cause of a pair that fails to match IRS records months after it was written down.

What are the five types of taxpayer identification numbers?

The Social Security number on Form SS-5, the employer identification number on Form SS-4, the individual taxpayer identification number on Form W-7, the adoption taxpayer identification number on Form W-7A, and the preparer tax identification number on Form W-12. A small employer meets three of the five in practice.

Which taxpayer identification number do I collect from a contractor?

Whichever one they certify, which depends on how they are organized. A sole proprietor gives a personal number or a business number if they have one; a partnership or corporation gives the entity number; a disregarded single-member company reports under its owner. Paying contractors correctly starts with getting that certification before the first payment.

Can an employee work using an ITIN?

No. It exists for federal tax reporting only, does not authorize employment in the United States, and confers no Social Security eligibility. IRS guidance tells employers not to accept one in place of a Social Security number for employee identification or for work, and employment eligibility is settled through the I-9 process instead.

How do I check that a name and taxpayer identification number match?

Through the free federal services. The IRS on-line matching program handles payees, taking 25 pairs on screen with immediate results or 100,000 by file within 24 hours. The Social Security Administration verifies employee names and numbers for wage reporting, 10 on screen or 250,000 by upload.

What happens if a 1099 has a missing or wrong taxpayer identification number?

It counts as an incorrect information return, priced by how quickly you fix it: $60 within 30 days, $130 by August 1, and $340 after that for returns required to be filed in 2026. A mismatch also produces a notice from the IRS that can lead to backup withholding, and the contractor filing process is where the correction gets made.

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