What Is a TIN on a 1099? Rules, B-Notices, and Penalties

The Taxpayer Identification Number on a 1099 is the nine-digit number that identifies each party to a reported payment — the payer and the payee — so the IRS can match the income a business reports against what the recipient puts on their tax return. For most individuals it is a Social Security Number; for businesses it is an Employer Identification Number. If the number is missing or incorrect, federal law requires the payer to withhold 24% of every payment and send it to the IRS.¹

Every 1099 form carries two TINs, one for the payer and one for the payee. The IRS runs an automated match: when a client files a 1099-NEC showing $5,000 paid to you, the system uses your TIN to check that $5,000 appears somewhere on your return.² The same mechanism runs across every 1099 variant: interest on a 1099-INT, dividends on a 1099-DIV, real estate proceeds on a 1099-S, payment app transactions on a 1099-K. When the number does not match IRS records, the discrepancy gets flagged automatically.

Which Number Belongs on Your 1099

Federal law recognizes several categories of TIN, and the one that belongs on a 1099 depends on who you are.³

A Social Security Number is what U.S. citizens and eligible residents use for personal income like freelance work or investment earnings.
An Employer Identification Number is used by businesses, partnerships, trusts, and other non-individual entities. An LLC taxed as a partnership or a corporation gives clients its EIN rather than the owner’s SSN.⁴
An Individual Taxpayer Identification Number is issued to people who have a federal tax filing obligation but are not eligible for an SSN, such as certain nonresident aliens and their dependents.³
An Adoption Taxpayer Identification Number is a temporary number for a child in the process of being adopted domestically, used until the child receives a permanent SSN.

For most freelancers and independent contractors, the practical choice is SSN versus EIN. Single-member LLCs that have not elected corporate taxation use the owner’s SSN, which catches many people off guard. If you would rather not hand clients your Social Security number, applying for an EIN on the IRS website is free and takes minutes.

How You Give Your TIN to a Payer

Before a client can put your TIN on a 1099, they collect it through Form W-9, “Request for Taxpayer Identification Number and Certification.” You enter your legal name exactly as it appears on your tax return, select your entity type, provide your TIN, and list a current mailing address.⁵

You also certify under penalty of perjury that your TIN is correct and that you are not currently subject to backup withholding. That certification shifts liability: once you have signed a W-9 with a wrong number, the payer has documentation that the error came from your side. Download the form from irs.gov rather than using a version emailed by a client, because altered or outdated copies circulate.

Some entities are exempt from backup withholding even though they still supply a TIN on the W-9. The common exempt payees are corporations, tax-exempt organizations under Section 501(a), government entities, and financial institutions.⁵ Individuals and most sole proprietors do not qualify.

What Happens if the TIN Is Missing or Wrong

When a payer does not have a valid TIN on file, federal law requires them to withhold 24% of every payment and send it to the IRS.¹ The One, Big, Beautiful Bill made that 24% rate permanent.⁶ Withholding continues on every payment until you supply a correct TIN.

Four situations trigger backup withholding: you never gave the payer a TIN, the IRS notified the payer that the TIN you provided is wrong, you failed to certify your TIN on the W-9, or the IRS determined you underreported income in a prior year.¹ The first two are the common ones, and both are avoidable by filling out the W-9 carefully.

B-Notices

When the IRS finds a filed 1099 with a TIN that does not match its records, it sends the payer a CP2100 or CP2100A notice listing every mismatched payee. The payer then sends you a “First B-Notice” and a blank W-9 asking you to correct the problem.⁷ If the same mismatch shows up again in a later year, a Second B-Notice follows, and at that point you may need to provide verification from the Social Security Administration or IRS rather than just resubmitting a W-9.

While you sort out a B-Notice, the payer must withhold 24% from your payments. Ignoring these notices is one of the fastest ways to lose a chunk of your income to withholding that a phone call could have prevented.

Getting the Withheld Money Back

Backup withholding is not a penalty. It is a prepayment of tax. When you file your return for the year the income was received, you report the withheld amount as federal income tax already paid, the same way W-2 withholding is reported.⁸ If it exceeds what you owe, the difference comes back as a refund. The catch is timing: your money sits with the IRS for months until you file, which can strain cash flow for freelancers and small businesses.

Penalties on the Payer for Wrong TINs

The consequences fall on payers too. Businesses that file 1099s with incorrect or missing TINs face per-form penalties under Section 6721 that escalate the longer the error goes unfixed.⁹ For returns due in 2026:

Corrected within 30 days: $60 per return.
Corrected after 30 days but by August 1: $130 per return.
Corrected after August 1, or never corrected: $340 per return.
Intentional disregard: $680 per return with no maximum cap.

Small businesses with average annual gross receipts of $5 million or less qualify for lower maximum penalties at each tier, though the per-return amounts are the same.¹⁰ TIN errors are explicitly excluded from the “inconsequential error” exception that forgives minor mistakes on information returns. A wrong Social Security number is never treated as inconsequential.

How Payers Can Verify a TIN Before Filing

The IRS offers a free online TIN Matching tool that lets payers check name-and-TIN combinations against IRS records before filing 1099s.¹¹ You can check TINs one at a time in an interactive session or upload a batch file. Using the service requires registration on the IRS Payer Account File and an active irs.gov login.

Running TIN Matching before filing catches mismatches that would otherwise turn into B-Notices and penalties months later. For any business issuing more than a handful of 1099s, the check takes minutes and prevents most of the withholding and correction problems described above.

A Note on the 2026 Reporting Threshold

The rules about TINs do not depend on how much you were paid, but the threshold for when a 1099-NEC has to be filed at all did change. Starting with payments made in 2026, the reporting threshold for Form 1099-NEC rose from $600 to $2,000, with future inflation adjustments.¹² Payments below the threshold still count as taxable income to the recipient; the change only affects the paperwork. Fewer forms filed means fewer chances for a TIN mismatch to surface, but it does not change what your TIN is or how it is used when a 1099 does get filed.

1
Office of the Law Revision Counsel. 26 USC 3406 – Backup Withholding
2
Internal Revenue Service. General Instructions for Certain Information Returns (2025)
3
Office of the Law Revision Counsel. 26 USC 6109 – Identifying Numbers
4
eCFR. 26 CFR 301.6109-1 – Identifying Numbers
5
Internal Revenue Service. Form W-9 (Rev. March 2024)
6
Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide
7
Internal Revenue Service. Backup Withholding “B” Program
8
Internal Revenue Service. Backup Withholding
9
Internal Revenue Service. Information Return Penalties
10
Internal Revenue Service. General Instructions for Certain Information Returns (2026)
11
Internal Revenue Service. Taxpayer Identification Number (TIN) Matching
12
Internal Revenue Service. Form 1099 NEC and Independent Contractors