Does Everyone Have a Tax ID Number? SSN, ITIN, EIN, ATIN & PTIN

The United States uses five tax identification number types, and which one applies to you depends on who you are and what you’re reporting. The Social Security Number (SSN) covers citizens and authorized workers. The Individual Taxpayer Identification Number (ITIN) covers people who owe federal tax but can’t get an SSN. The Employer Identification Number (EIN) covers businesses and other entities. Two narrower numbers round out the list: the Adoption Taxpayer Identification Number (ATIN) for pending adoptions, and the Preparer Tax Identification Number (PTIN) for paid tax preparers. Federal law requires you to put the correct identifying number on every return or statement you file.¹

All five are nine digits (except the PTIN, which is issued in its own format), but they come from different agencies, serve different purposes, and are obtained through different forms.

Social Security Number

The SSN is issued by the Social Security Administration, not the IRS, and it stays with you for life.² It’s the primary tax ID for U.S. citizens and noncitizens authorized to work in the country. You use it to file returns, report wages, and later claim Social Security benefits.

Most people get their SSN at birth. Hospitals ask parents during birth registration whether they want to request a number; if they say yes, the information flows through the state vital records office to the SSA.³ The card usually arrives within three to ten weeks. Parents who skip the hospital step have to file Form SS-5 separately.⁴

Replacement cards are capped at three per calendar year and ten in a lifetime. Cards reissued for a legal name change or updated work-authorization status don’t count against those limits.⁴

Individual Taxpayer Identification Number

If you have a federal tax obligation but aren’t eligible for an SSN, the IRS issues an ITIN instead. It’s available to nonresident aliens, resident aliens, and their spouses or dependents.⁵ An ITIN follows the same nine-digit layout as an SSN but always starts with a 9.⁶

An ITIN is strictly for tax filing. It does not authorize you to work in the United States, and it does not make you eligible for Social Security benefits.⁷

You apply on Form W-7, and in most cases you must submit your federal tax return in the same package rather than filing it separately.⁵ If you don’t want to mail original passports or other identity documents, a Certifying Acceptance Agent can verify them on the spot, or you can apply at an IRS Taxpayer Assistance Center offering ITIN services or a participating VITA site.⁸

ITINs can expire. If yours isn’t used on a federal tax return for three consecutive years, it expires on December 31 of that third year.⁹ Renewal uses the same Form W-7 with the renewal box checked; no tax return is required for a renewal-only application. You don’t need to renew if your expired ITIN only appears on information returns like a 1099 rather than on your own filed return.

Employer Identification Number

The EIN is the tax ID for businesses, nonprofits, estates, trusts, and other entities. The IRS issues it for free through Form SS-4.¹⁰ Applying online returns the number immediately; fax and mail applications take longer.

Not every business needs an EIN. A sole proprietor with no employees and no excise tax liability can report business income using a personal SSN.¹¹ You do need one once any of the following applies:

You hire at least one employee and need to report payroll taxes.
You open a Keogh or Solo 401(k) retirement plan.
You file excise tax returns, such as for alcohol, tobacco, or firearms.
You change your business structure by incorporating, forming a partnership, or creating an LLC.
You buy or inherit an existing business; the previous owner’s EIN can’t carry over.

The online EIN tool operates Monday through Friday from 6:00 a.m. to 1:00 a.m. Eastern, Saturday from 6:00 a.m. to 9:00 p.m., and Sunday from 6:00 p.m. to midnight. Only one EIN per responsible party per day is allowed.¹²

Adoption Taxpayer Identification Number

An ATIN is a temporary number for a child in a pending domestic adoption, so the adoptive parents can claim the child as a dependent before an SSN is issued. You qualify to request one if the child was placed in your home by an authorized agency, you can’t obtain the child’s existing SSN despite reasonable effort, and the child is eligible to be claimed as your dependent. The form is W-7A.¹³

Preparer Tax Identification Number

Anyone who prepares or helps prepare federal tax returns for pay, including enrolled agents, must have a valid PTIN before working on any return. You apply or renew through the IRS online system or by mailing Form W-12, and the fee is $18.75.¹⁴ A PTIN must be renewed every year; a 2026 PTIN is required before preparing any 2026 returns.

Who Doesn’t Need a Tax ID

Not everyone requires a U.S. tax identification number:

Foreign nationals who live outside the United States and earn no U.S.-source income have no filing obligation and don’t need one.
Newborns don’t have an SSN until parents request one, either through the hospital’s Enumeration at Birth process or by filing Form SS-5.
Sole proprietors with no employees, no excise tax liability, and no retirement plan can use a personal SSN instead of an EIN.¹¹

Even where the law doesn’t require a number, going without one creates practical friction. Many banks won’t open a business account without an EIN, and without an SSN or ATIN for a child, you can’t claim child-related tax credits for that year.

What It Costs to Have the Wrong Tax ID

Missing, incorrect, or expired numbers carry real money consequences.

Backup Withholding

If you don’t give a correct taxpayer identification number to a payer such as a bank, brokerage, or client, the payer must withhold 24 percent of your payments and send it to the IRS.¹⁵ You can recover it later by filing a return with a valid TIN, but the cash is out of your hands in the meantime.

Lost Tax Credits

Some credits require a specific ID type. The Child Tax Credit, worth up to $2,200 per qualifying child, requires the child to have an SSN valid for employment. A child who has only an ITIN doesn’t qualify for the full credit and instead may qualify for the Credit for Other Dependents, capped at $500.¹⁶ The gap is up to $1,700 per child, per year.

Delays and Penalties

Filing with an expired ITIN can hold up your refund for weeks or months while the IRS processes the renewal.⁹ On the payer side, failing to include a correct TIN on an information return can trigger per-return penalties under federal law, with amounts adjusted annually for inflation.¹⁷

Processing Times

How fast a number arrives depends on the type and how you filed:

SSN: usually 7–10 business days once the SSA has all needed documentation; mail applications can run two to four weeks.¹⁸
ITIN: about seven weeks outside filing season; nine to eleven weeks during peak season (January 15 through April 30) or when applying from overseas.⁸
EIN online: issued immediately at the end of the application.¹²
EIN by fax: usually about four business days. By mail: four to five weeks.

1
Office of the Law Revision Counsel. 26 USC 6109 – Identifying Numbers
2
Social Security Administration. Social Security Number and Card
3
Social Security Administration. State Processing Guidelines for Enumeration at Birth
4
Social Security Administration. Application for Social Security Card – Form SS-5
5
Internal Revenue Service. Individual Taxpayer Identification Number (ITIN)
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Internal Revenue Service. Taxpayer Identification Numbers (TIN)
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eCFR. 26 CFR 301.6109-1 – Identifying Numbers
8
Internal Revenue Service. How to Apply for an ITIN
9
Internal Revenue Service. How to Renew an ITIN
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Internal Revenue Service. Employer Identification Number
11
Internal Revenue Service. Single Member Limited Liability Companies
12
Internal Revenue Service. Get an Employer Identification Number
13
Internal Revenue Service. Instructions for Form W-7A
14
Internal Revenue Service. PTIN Requirements for Tax Return Preparers
15
Internal Revenue Service. Backup Withholding
16
Internal Revenue Service. Child Tax Credit
17
Office of the Law Revision Counsel. 26 USC 6721 – Failure to File Correct Information Returns
18
Social Security Administration. How Long Will It Take to Get a Social Security Card