What Is a W-9 for Subcontractors?

Form W-9 is the IRS form a subcontractor fills out to give you their legal name, tax classification and taxpayer identification number (TIN). You keep it on file; it isn't sent to the IRS. You use it to decide whether the sub needs a Form 1099-NEC and to fill one out correctly.

What does a W-9 do for a contractor?

A W-9 is how you get the information you'll need at year end, before you need it. The IRS describes it as the form used by people "required to file information returns with the IRS to get the payee's" correct name and TIN. In plain terms: every sub you pay should hand you one, and you file it in a folder (or your bookkeeping system), not with the government.

You'll use it in January, when you decide who gets a Form 1099-NEC. For payments made in 2026, a 1099-NEC is required when you paid an unincorporated sub $2,000 or more during the year. For 2025 payments, the threshold was $600. Collect a W-9 from every sub regardless, because you won't know in March who'll cross the line by December.

What's on a W-9, line by line?

How to read the tax classification box

• Individual/sole proprietor or single-member LLC: gets a 1099-NEC if you paid them $2,000 or more in 2026.
• Partnership, or LLC with code P: gets a 1099-NEC.
• C corporation or S corporation, or LLC with code C or S: generally no 1099-NEC, because payments to corporations are generally exempt. Attorneys are the main exception.
• Box checked doesn't match what you know? If a one-man crew checks "C corporation" but invoices under his own name with his SSN, ask before you rely on it. A CPA can help you document the decision.

When should you ask a subcontractor for a W-9?

Before the first payment, ideally when you onboard the sub along with their certificate of insurance and license. That's when you hold the cards: the sub wants the work and the check. Once the job is paid and the sub has moved on, you're chasing paperwork in January with a filing deadline coming.

1. 1

   Send the current form.

   Download Form W-9 from irs.gov so you're using the current revision (March 2024), not a copy saved on the office computer years ago.

2. 2

   Check it when it comes back.

   Is it signed and dated? Is a TIN entered? Is one classification box checked? Does the name on line 1 look like it matches the TIN type (a person's name with an SSN, a business with an EIN)?

3. 3

   Record the classification in your books.

   Flag the vendor as a 1099 vendor (or not) in QuickBooks or your bookkeeping system so payments are tracked from day one.

4. 4

   Store it securely.

   A W-9 holds a Social Security number. Keep it where only the people who need it can see it, not in a shared inbox.

5. 5

   Ask for a new one when things change.

   If the sub incorporates, changes their business name or gets an IRS notice that their TIN is wrong, get a fresh W-9.

What if a sub refuses to fill out a W-9?

Then you're required to backup-withhold. The IRS's requester instructions put it plainly: "The backup withholding rate is 24% for reportable payments," and it applies when a payee fails to furnish a TIN or when the IRS notifies you that a TIN is incorrect. Withholding continues until the problem is fixed. If you don't withhold when you should, the IRS says you may become liable for the uncollected amount.

The 2025 tax law raised the backup withholding threshold along with the 1099-NEC threshold: for payments made after December 31, 2025, it ties to the same $2,000 level. Rather than run backup withholding for one sub, most contractors make a signed W-9 a condition of the first check. Write it into your subcontract agreement.

Can you verify a subcontractor's TIN?

Yes. The IRS runs a TIN Matching e-service that lets payers who file information returns check a name and TIN combination against IRS records before filing. It requires registering for IRS e-Services. Matching before you file reduces the chance of a mismatch notice, and the IRS says verified matches can help show reasonable cause if penalties come up.

W-9 vs. W-4 vs. 1099: what's the difference?

If you find yourself collecting W-9s from people you schedule, supervise and equip like staff, the form isn't the issue; the classification is. See W-2 vs. 1099 and the IRS common-law control test before you go further.

Common W-9 mistakes

• Paying first, collecting later. The single most common reason 1099s are late or wrong.
• Accepting an unsigned form. The certification in Part II is what makes the TIN usable.
• Not reading the classification box. It's the difference between sending a 1099 and not.
• Emailing W-9s around in plain text. It's a document with an SSN on it; treat it that way.
• Never updating. A sub who incorporated last spring may now be exempt, or may have a new EIN.