To verify a W-9, review the form field by field for a legible name, TIN, tax classification, and signature, then run the name-TIN combination through the IRS’s free TIN Matching program on the e-Services portal before you file any 1099s. The interactive tool checks up to 25 name-TIN pairs on screen; the bulk option handles up to 100,000 in a single upload.1Internal Revenue Service. Taxpayer Identification Number (TIN) On-Line Matching Catching a mismatch now is cheaper than fixing it after the IRS sends you a CP2100 notice and you have to start withholding 24 percent from every payment.
Check the Form Itself First
Before you touch any IRS tool, read the W-9 the payee handed you.
Line 1 — Legal name. This must match exactly what the payee registered with the Social Security Administration (for individuals) or the IRS (for businesses). A trade name or DBA does not belong here; it goes on Line 2. The IRS matches against Line 1, not Line 2.2Internal Revenue Service. Form W-9 (Rev. March 2024)
Line 3a — Federal tax classification. Individual/sole proprietor, C corporation, S corporation, partnership, trust/estate, or LLC. The classification decides which name-TIN pair the IRS expects. A single-member LLC that is a disregarded entity, for instance, uses the owner’s name and SSN (or EIN), not the LLC’s name.2Internal Revenue Service. Form W-9 (Rev. March 2024)
Part I — Taxpayer Identification Number. A nine-digit number: an SSN for most individuals, an EIN for most businesses, or an ITIN where applicable.3eCFR. 26 CFR 301.6109-1 – Identifying Numbers Every digit needs to be legible. If any digit is unclear or a number is missing, ask the payee to resubmit on a fresh Form W-9 from the IRS website.4Internal Revenue Service. About Form W-9, Request for Taxpayer Identification Number and Certification
Signature and date. The form must be signed under penalties of perjury by the payee or an authorized signer. Without that signature, you cannot rely on the W-9 to avoid backup withholding.5Internal Revenue Service. Instructions for the Requester of Form W-9
Who Can Use the IRS TIN Matching Program
TIN Matching is not open to the general public. You qualify if you are a payer (or a payer’s authorized agent) who files information returns such as Forms 1099, and your organization must appear on the IRS Payer Account File database.6Internal Revenue Service. Taxpayer Identification Number (TIN) Matching If you have never filed an information return, you will not have access until you do.
Register for IRS e-Services
A responsible official at your organization registers through the IRS website and completes identity verification, which requires personal details including legal name and Social Security Number.7Internal Revenue Service. e-Services Registration Every person in your organization who will run TIN matches registers individually. Once the IRS verifies the information, it mails a confirmation to the registrant’s address on file. After you activate the account, log in and open the TIN Matching application inside the e-Services dashboard.8Internal Revenue Service. Taxpayer Identification Number (TIN) Matching Tools
Run an Interactive or Bulk Match
Two options, same underlying database:
- Interactive matching returns results on screen for up to 25 name-TIN pairs at a time. Good for onboarding a small number of new vendors.
- Bulk matching takes a formatted text file of up to 100,000 pairs and returns a downloadable response file within 24 hours.1Internal Revenue Service. Taxpayer Identification Number (TIN) On-Line Matching
Either way, enter the TIN and the legal name exactly as they appear on Line 1. Small differences trip the match. A middle initial on the W-9 that is not in IRS records, an added “Inc.” that does not belong to the registered name — either can produce a mismatch even when the number itself is right.
Read the Result Codes
The system returns a single-digit code for each pair:
- Code 0. The name and TIN match IRS records. Nothing more to do.
- Code 1. The TIN was not found. Either the number is wrong or it has not yet been assigned.
- Code 6. Duplicate submission in the same session; not processed.
Other codes flag a name-TIN mismatch (the TIN exists but belongs to a different name) or a formatting error in what you submitted. Anything other than Code 0 means follow up with the payee before you file a 1099 under that combination.
What Happens If You File With a Bad TIN
If a mismatch slips through and lands on an information return, the IRS sends you a CP2100 or CP2100A notice listing the affected payees. That starts a two-stage correction process.
On a First B-Notice, you send the payee a notice and a blank Form W-9 asking for corrected information. If the payee does not respond, backup withholding must begin no later than 30 business days after you received the CP2100 or CP2100A.9Internal Revenue Service. Understanding Your CP2100 or CP2100A Notice
If the same payee appears again on a CP2100 or CP2100A within three calendar years, you send a Second B-Notice. This time a fresh W-9 is not enough. The payee has to contact the IRS or SSA directly to verify the correct name-TIN combination before you can stop withholding.10Internal Revenue Service. Backup Withholding for Missing and Incorrect Name/TINs
Backup withholding also applies when a payee gives you no TIN at all, refuses to provide a W-9, or has not certified they are exempt. The rate is 24 percent of reportable payments for 2026.11Internal Revenue Service. Publication 15 (2026) If you fail to withhold when required, you can be held personally liable for the uncollected tax.12Internal Revenue Service. Instructions for the Requester of Form W-9 The amounts you withhold are reported on Form 945, due January 31 of the following year, or February 10 if all deposits were made on time.13Internal Revenue Service. Instructions for Form 945 (2025) The underlying rule is at 26 U.S.C. § 3406.14Office of the Law Revision Counsel. 26 USC 3406 – Backup Withholding
When a W-9 Is the Wrong Form
A W-9 is only for U.S. persons, which includes U.S. citizens living abroad and resident aliens. A nonresident alien or foreign entity should give you a Form W-8BEN (or another form in the W-8 series) instead.15Internal Revenue Service. Instructions for Form W-8BEN Payments to nonresident alien contractors can be subject to 30 percent withholding under IRC § 1441 unless a tax treaty sets a lower rate. If you receive a W-9 from someone whose status you are unsure about, confirm before you accept the form. Taking the wrong form leaves you exposed to under-withholding liability or subjects the payee to over-withholding.
Penalties for Filing Incorrect Information Returns
A wrong name-TIN combination on a 1099 carries per-return penalties under 26 U.S.C. § 6721. For returns due in 2026:16Internal Revenue Service. Information Return Penalties
- Corrected within 30 days: $60 per return.
- Corrected after 30 days but by August 1: $130 per return.
- Filed after August 1 or not filed at all: $340 per return.
- Intentional disregard: $680 per return, with no annual cap.
Penalties apply separately to each incorrect return and each incorrect payee statement, so the totals climb fast when you have many contractors. States may add their own penalties for late or incorrect 1099 filings; check your state tax agency if you file at the state level. Running a TIN match before you file is the cheapest way to keep this list irrelevant to you.