What Is an FTN Number? Types, Uses, and Penalties

An FTN number is informal shorthand for a federal Taxpayer Identification Number, which the IRS officially calls a TIN. It’s the nine-digit number the IRS uses to tie you or your business to federal tax records, and every person or entity that files a federal return needs one.¹ The IRS itself does not use “FTN” in its forms or publications; banks, foreign governments, and some financial paperwork use the label colloquially, but the concept is the same.

Depending on who you are, your FTN will be a Social Security Number, an Individual Taxpayer Identification Number, or an Employer Identification Number. The Social Security Administration issues SSNs. The IRS issues the rest.

Which TIN You Actually Need

Social Security Number

The SSN is the default FTN for U.S. citizens and noncitizens authorized to work in the country. You need one to take a job, file taxes, open most financial accounts, apply for a loan, or claim government benefits.² If you already have an SSN, that is your federal taxpayer number; you don’t need anything else on the individual side.

Individual Taxpayer Identification Number

An ITIN is the IRS-issued nine-digit number for people who have a federal tax filing obligation but aren’t eligible for an SSN. That group typically includes nonresident aliens with U.S. tax obligations, resident aliens who can’t get an SSN, and their spouses or dependents claimed on a return.³

An ITIN exists strictly for federal tax purposes. It does not authorize work in the United States, change your immigration status, qualify you for Social Security benefits, or make you eligible for the Earned Income Tax Credit.³

Employer Identification Number

An EIN is the FTN for business entities. Corporations, partnerships, estates, trusts, and nonprofits all need one.⁴ Sole proprietors can often use their SSN for business taxes, but the IRS requires an EIN once you hire employees, operate as a partnership or corporation, pay excise taxes, change your business structure, or administer a retirement plan, trust, or estate.⁵ Many sole proprietors get one anyway to keep their SSN off contracts and vendor forms.

Two Narrower Numbers

Two other TINs cover specialized situations. An Adoption Taxpayer Identification Number (ATIN) is a temporary number for a child being adopted when the adoptive parents can’t get the child’s SSN, applied for on Form W-7A.⁶ A Preparer Tax Identification Number (PTIN) is required only for people who prepare federal returns for pay and must be renewed each year.⁷ Neither is what someone means when they ask you for an “FTN.”

When You’re Required to Have One

Filing a federal return is the obvious trigger. Without a TIN the IRS can’t process your return and won’t issue a refund. Employers need it to withhold and report your wages, and financial institutions need it to open accounts and report interest.

Freelance and gig income brings its own triggers. Third-party payment platforms like Venmo and PayPal must file Form 1099-K reporting payments to the IRS when a payee’s gross payments exceed $20,000 and the number of transactions exceeds 200 in a calendar year, and they need your TIN to do it.⁸ Fail to give a correct TIN to a payer, and 24% backup withholding kicks in on your payments until the issue is fixed.⁹

How to Apply

For an SSN, complete Form SS-5 and submit at least two documents proving your age, identity, and citizenship or immigration status to the Social Security Administration. If you’re 12 or older and have never had an SSN, you have to apply in person.¹⁰

For an ITIN, file Form W-7 with documents proving both foreign status and identity.¹¹ You can mail it in with your tax return and original identification, visit an IRS Taxpayer Assistance Center, or use an IRS-authorized Acceptance Agent who reviews your documents so you don’t have to mail originals. Processing runs about 7 weeks, or 9 to 11 weeks during tax season (January 15 through April 30) and for applications from overseas.³

For an EIN, businesses file Form SS-4. The IRS online application is free and issues the number immediately upon approval, and it’s available to applicants with a legal residence or principal business location in the United States or U.S. territories.¹² Fax applications generally process in about four business days; mailed applications take roughly four weeks.⁵

ITINs Expire

An ITIN is not permanent. If you don’t use it on a federal return for three consecutive years, it expires automatically on December 31 of that third year, and filing with an expired ITIN can delay any refund until you renew.¹³ Renewal uses the same Form W-7 and the same document rules as the original application, submitted by mail, in person, or through an Acceptance Agent. The IRS recommends renewing before your next filing to avoid processing delays. SSNs and EINs don’t expire this way.

What It Costs to Skip It

The penalties for missing or wrong TINs stack quickly. Individuals face a $50 penalty for each missing TIN required on a return or statement, capped at $100,000 per calendar year.¹⁴

Businesses filing 1099s and other information returns with missing or incorrect TINs face a sliding penalty:

$60 per return if corrected within 30 days
$130 per return if corrected by August 1
$340 per return if not corrected after August 1
$680 per return for intentional disregard, with no maximum cap

Those penalties apply separately for failing to file a correct information return and for failing to furnish a correct payee statement, so the same error can be charged twice.¹⁵ The IRS may reduce or remove penalties for reasonable cause.

Then there’s the cash-flow hit. Backup withholding at 24% applies whenever a payee doesn’t give a correct TIN, and that money goes straight to the IRS. You only recover it by filing a return and claiming it back.⁹ For a freelancer already waiting to be paid, losing a quarter of every check is a bigger problem than the paperwork was.

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Internal Revenue Service. Taxpayer Identification Numbers (TIN)
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Social Security Administration. Request a Social Security Number for the First Time
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Internal Revenue Service. Individual Taxpayer Identification Number (ITIN)
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Internal Revenue Service. About Form SS-4, Application for Employer Identification Number
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Internal Revenue Service. Get an Employer Identification Number
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Internal Revenue Service. Adoption Taxpayer Identification Number
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Internal Revenue Service. IRS Reminds Tax Pros to Renew PTINs for the 2026 Tax Season
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Internal Revenue Service. IRS Issues FAQs on Form 1099-K Threshold Under the One, Big, Beautiful Bill; Dollar Limit Reverts to $20,000
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Internal Revenue Service. Topic No. 307, Backup Withholding
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Social Security Administration. Application for a Social Security Card
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Internal Revenue Service. Form W-7 – Application for IRS Individual Taxpayer Identification Number
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Internal Revenue Service. Instructions for Form SS-4 – Application for Employer Identification Number
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Internal Revenue Service. How to Renew an ITIN
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Internal Revenue Service. Information About Your Notice, Penalty and Interest
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Internal Revenue Service. Information Return Penalties