To verify a W-9, check that line 1 shows the name on the vendor's tax return, exactly one tax classification is selected, the TIN is a nine-digit SSN or EIN in the right box, the form is the current IRS revision, and it is signed and dated if your policy requires it. Then, if you are enrolled, confirm the name and TIN pair with IRS TIN Matching.
What does each line on a W-9 mean?
The current Form W-9 has seven numbered lines plus two parts. Here is what each one should hold.
| Line | What it should contain | What often goes wrong |
|---|---|---|
| 1. Name of entity/individual | The name on the vendor's income tax return. An entry is required. | Brand name instead of legal name |
| 2. Business name/disregarded entity name | A trade name, DBA, or the name of a disregarded LLC | Left blank, so invoices in the brand name don't match |
| 3a. Federal tax classification | Exactly one box. LLCs taxed as a corporation or partnership tick LLC and write C, S or P | Two boxes ticked, or LLC ticked with no letter |
| 3b. Foreign partners, owners or beneficiaries | Only for partnerships, trusts and estates in specific cases | Ticked by mistake by an ordinary company |
| 4. Exemptions | Exempt payee code and FATCA code, if any | Codes entered without reason |
| 5 and 6. Address | Street, city, state and ZIP | Differs from your vendor setup form |
| 7. Account numbers | Optional | |
| Part I. TIN | SSN or EIN in the matching box | EIN typed in the SSN boxes |
| Part II. Certification | Signature and date | Unsigned, or undated |
Line 4 deserves a second look. An exempt payee code can change whether you file a Form 1099 for this vendor, so check any code against the list in the IRS instructions rather than accepting it as entered.
How do you check the name and TIN?
The name and TIN are checked by the IRS as a pair, so they have to belong together.
- Individuals and sole proprietors put their own name on line 1 and any business or DBA name on line 2. A sole proprietor with an EIN may enter either their SSN or their EIN.
- Corporations and partnerships give the entity's legal name and its EIN.
- Single-member LLCs that are disregarded put the owner's name on line 1, the LLC's name on line 2, and tick the owner's classification, not the LLC box. The TIN is the owner's SSN, or the owner's EIN if they have one.
- LLCs taxed as a corporation or partnership use the LLC's own name and EIN.
Then check the shape of the number. An SSN is nine digits written XXX-XX-XXXX. An EIN is nine digits written XX-XXXXXXX. Eight digits, ten digits or a letter means a typo, and the form goes back.
If the TIN space says "Applied For", the vendor has applied for a number or is about to. For most vendor payments, backup withholding applies until they give you the TIN, so put a follow-up date on it.
Does a W-9 need to be signed?
Less often than people think. The W-9 instructions say a signature is generally not required for payments such as rents, royalties and nonemployee services, as long as the vendor gives a correct TIN. A signature is required if the vendor was previously notified of an incorrect TIN, and a requester may ask for one anyway.
Most AP teams take the simple route and require every W-9 to be signed and dated. That is a reasonable policy. Just apply it consistently, and send the form back when the signature or date is missing.
Which W-9 revision is current?
At the time of writing, the current form is Form W-9 (Rev. March 2024). That revision added line 3b and clarified how disregarded entities fill in lines 1 and 2. The IRS has also posted a draft revision dated June 2026 on its draft forms page, and drafts must not be used.
Revisions change, so check the About Form W-9 page on irs.gov before you update your vendor packet. If a new vendor sends an old revision, asking for the current one is a quick, reasonable request.
How does IRS TIN Matching work?
A format check tells you the TIN is shaped correctly. It cannot tell you the TIN belongs to that vendor. The IRS TIN Matching program can.
TIN Matching is for payers, and their authorized agents, who file information returns subject to backup withholding, such as many Forms 1099. You need an IRS online account and an approved application. Once you are in, you submit a name and TIN combination and the IRS tells you whether it matches its records. Interactive and bulk options are available, and the results must be kept confidential.
A mismatch is usually a name problem: a brand name on line 1, or a disregarded LLC's name paired with the owner's SSN. Ask the vendor for a corrected W-9 before the first payment.
What is backup withholding?
Backup withholding is tax you hold back from a payment and send to the IRS. The IRS states the current rate is 24 percent. It generally applies when a vendor does not give you a TIN, or when the IRS tells you the name and TIN combination is incorrect.
It covers payments such as interest, dividends, rents, royalties and independent contractor fees. Getting the W-9 right before the first payment is much easier than starting withholding later.
One more case: foreign persons may not provide a Form W-9. A foreign vendor should give you the right Form W-8 instead.
What are the common W-9 mistakes, and how do you catch them?
The mistakes that come up most are a brand name on line 1, a disregarded LLC using its own name and ticking the LLC box, an EIN typed in the SSN boxes, two digits swapped, an old revision, and a foreign vendor sending a W-9 instead of a W-8. Run this checklist on every new form:
- Line 1 is the name on the vendor's tax return
- Line 2 holds the DBA or disregarded LLC name, if any
- Exactly one classification on line 3a, with a letter if LLC is ticked
- Line 3b and line 4 only filled in when they apply
- Address matches your vendor setup form
- TIN is nine digits, in the box that fits the classification
- Signed and dated, if your policy or the IRS rules require it
- Current revision, checked on irs.gov
- Name and TIN confirmed with TIN Matching, if enrolled
- Name matches the certificate of insurance and bank details
How SensiDocs helps
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