W-9 Forms for Sole Proprietors and LLCs: Who Signs What
Sole proprietor or LLC contractor? Learn exactly how to fill out a W-9 correctly, avoid TIN mismatches, and stay IRS-compliant when paying contractors.
1Why Business Structure Changes How a W-9 Is Completed
A W-9 isn't one-size-fits-all — the correct way to complete it depends entirely on how a contractor's business is legally structured. Sole proprietors, single-member LLCs, multi-member LLCs, and S-corps each have different requirements for Line 1, Line 2, and the federal tax classification checkbox. Getting these wrong is one of the most common causes of TIN mismatch notices from the IRS, which can trigger backup withholding at 24% on future payments.
2Sole Proprietors: Use the Owner's Name, Not the Business Name
A sole proprietor must enter their personal legal name on Line 1 of the W-9 — not the name of their DBA or business. If they operate under a trade name, that business name goes on Line 2. The Social Security Number or EIN on the form must match the name on Line 1 exactly as it appears in IRS records. Mismatches here are a leading cause of 'B notices' (IRS Notice CP2100), which obligate you as the payer to begin backup withholding.
3Single-Member LLCs: Disregarded Entity Rules Catch Businesses Off Guard
By default, a single-member LLC is a 'disregarded entity' for federal tax purposes, meaning the IRS treats it as the individual owner. On the W-9, the owner's personal name still goes on Line 1, the LLC name on Line 2, and the 'Individual/sole proprietor or single-member LLC' box should be checked — not 'Limited liability company.' The TIN entered should match whichever name is on Line 1, which in most cases is the owner's SSN. Many single-member LLC owners incorrectly check the LLC box and enter their EIN, creating a mismatch.
4Multi-Member LLCs and LLCs Taxed as S-Corps or C-Corps
A multi-member LLC is treated as a partnership by default, so the LLC's legal name goes on Line 1 and the EIN is the correct TIN. If the LLC has elected to be taxed as an S-corporation or C-corporation by filing Form 2553 or 8832, the contractor checks the 'Limited liability company' box and enters 'S' or 'C' in the classification field. Payments made to LLCs taxed as S-corps or C-corps generally do not require a 1099-NEC, which is a meaningful compliance difference for small businesses doing the reporting.
5How to Verify You Have the Right Information Before You Pay
Before issuing any payment to a new contractor, run their TIN and name combination through the IRS TIN Matching program (available free through the IRS e-Services portal). This confirms that the name and TIN combination on the W-9 matches IRS records before you file a 1099-NEC — not after. Catching a mismatch upfront avoids the $310-per-form penalty for filing a 1099 with an incorrect TIN. Tools like W-9 Nudge can flag structural inconsistencies in a submitted W-9 before a payment is processed, adding a practical first line of defense.
6When to Ask a Contractor to Resubmit Their W-9
Request a corrected W-9 any time a contractor changes their business structure, switches from an SSN to an EIN, forms an LLC, or elects corporate tax treatment. You should also request a new form if you receive an IRS B notice indicating a TIN mismatch on a prior filing. Keep a dated copy of every version of a contractor's W-9 — IRS regulations require you to retain W-9 forms for at least four years after the last tax year in which a return was filed using that information.
7Building a Reliable Collection Process for Mixed Contractor Types
If your contractor base includes a mix of sole proprietors, single-member LLCs, and corporate entities, a standardized collection process reduces errors significantly. A digital W-9 collection tool with guided form fields can prompt contractors to select the correct tax classification based on their stated business type, reducing the blank-field and wrong-checkbox errors that paper forms invite. Segment your vendor records by entity type so you can quickly identify at year-end which contractors require a 1099-NEC, which are exempt, and which need TIN verification before filing.
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Disclaimer: This post is for general informational purposes only. W‑9 Nudge does not provide tax, legal, or accounting advice. Consult a qualified professional for guidance specific to your situation.