Guide
What Is IRS Form W-9?
By Keelstar Team · Updated July 11, 2026
The short answer
IRS Form W-9, Request for Taxpayer Identification Number and Certification, is the standard form U.S. persons and U.S. entities use to provide their taxpayer identification number (TIN) and certify their tax status to a payer. You collect it before making reportable payments so you have the legal name, address, federal tax classification, and TIN needed for Form 1099 filing. The payee certifies under penalties of perjury that the TIN is correct, they are a U.S. person, and whether they are subject to backup withholding. A complete, signed W-9 on file is your primary evidence for correct information return reporting.
Purpose of Form W-9
Form W-9 exists so payers can obtain a payee's correct taxpayer identification number and tax certifications before making reportable payments. You use the data to prepare Forms 1099-NEC, 1099-MISC, and other information returns. Without a W-9, you lack the legal name, address, TIN, and federal tax classification needed to file accurately — and you may face backup withholding obligations if the payee does not certify correctly.
Key sections of the form
The current W-9 collects the payee's name, business name if applicable, federal tax classification, exemptions from backup withholding and FATCA reporting, address, and TIN. Part II is the certification under penalties of perjury — signature and date are required. A form missing any of these fields is incomplete and should not be treated as valid for payment release.
- Line 1: Legal name as shown on tax return
- Line 3: Federal tax classification (individual, LLC, C-corp, etc.)
- Part I: SSN or EIN
- Part II: Signature, date, and backup withholding certification
Who provides a W-9 vs a W-8
U.S. persons and U.S. entities complete Form W-9. Foreign individuals and entities use Form W-8BEN, W-8BEN-E, or other W-8 variants depending on their status. If a vendor operates outside the U.S. and claims foreign status, do not accept a W-9 — route them to the correct W-8 form and document your determination.
Why AP teams collect W-9s before payment
Collecting the W-9 at onboarding — not at year-end — prevents a cascade of problems: unreportable payments, TIN mismatches on filed 1099s, emergency vendor outreach in January, and backup withholding triggered by missing or incorrect data. Treat the W-9 as a payment prerequisite alongside banking details and purchase order setup.
Common W-9 errors AP should catch
Incomplete forms are the norm when vendors self-complete without guidance. Watch for missing signatures, blank TIN fields, wrong entity classification (especially LLCs), trade names on line 1 instead of legal names, and outdated form revisions. Validate at intake rather than discovering errors when the IRS sends a CP2100 notice.
- Unsigned or undated forms
- SSN provided where an EIN is expected for an LLC or corporation
- Disregarded entity status not indicated when required
- Exempt payee box checked without supporting documentation
How W-9 connects to 1099 filing
The name and TIN on your 1099 must match what the payee certified on the W-9 and what IRS records show. Federal tax classification on the W-9 tells you whether a payment is reportable at all — corporations are often exempt from 1099-NEC, while sole proprietors and LLCs taxed as partnerships generally are not. Your W-9 file is the source document for every information return you issue.
Frequently asked questions
- Who must complete Form W-9?
- U.S. persons — including citizens, resident aliens, and entities formed under U.S. law — provide a W-9 to payers who will report payments on Form 1099 or other information returns. Foreign persons use the W-8 series instead.
- Is Form W-9 submitted to the IRS?
- No. The payee completes the W-9 and returns it to you, the payer. You retain it for your records and use the TIN and certification when filing information returns. Do not send completed W-9s to the IRS unless specifically requested in an audit.
- What TIN goes on line 1 of the W-9?
- Line 1 is the name as shown on the income tax return — the legal name for entities or the individual name for sole proprietors. Line 2 is for a business or disregarded entity name if different. The TIN (SSN or EIN) goes in Part I.
- How long should we keep W-9s on file?
- Retain W-9s for at least four years after the year the related 1099 was filed, though many U.S. finance teams keep them longer — often for the life of the vendor relationship plus the retention period. Store them securely with access controls.
Related guides
Put this into a monitored workflow
W-9 Collector handles this continuously — with reminders and an audit trail.