Form W-9: get it before the first check, not after the first 1099

A W-9 costs nothing and takes two minutes. Not having one costs you 24 cents on every dollar you pay that subcontractor. That is not a penalty and it is not negotiable: the IRS states that where a payee fails to provide a correct taxpayer identification number, "the payer is required to withhold at the current rate of 24 percent."

The word to notice in that sentence is payer. You are the payer. If you paid your framing sub in full without a TIN on file, the IRS does not go looking for the sub — it looks at the business that was supposed to withhold and did not.

So the rule for a construction business is short: the W-9 comes before the first check, in the same folder as the certificate of insurance and the signed subcontract. Both of those are exactly what stops the first check before the billing run even starts: invoicing for contractors: the billing run, in order.

What Form W-9 actually is

Form W-9, Request for Taxpayer Identification Number and Certification, is how a business asks a payee for the number it will later put on an information return. The IRS describes its purpose as providing "your correct Taxpayer Identification Number (TIN) to the person who is required to file an information return with the IRS."

The current revision on the IRS forms page is Rev. 3-2024 (March 2024).

Three things to understand about it:

• It is not filed with the IRS. You keep it in your records. What goes to the IRS is the 1099 you file later.
• It has no expiration date. But it becomes wrong the moment your sub incorporates, changes name, or changes TIN — and a wrong W-9 is worse than none, because it gives you false confidence.
• A TIN can be an SSN, an EIN or an ITIN. The IRS lists all three: "A TIN includes your Social Security Number (SSN), Employer Identification Number (EIN), or Individual Taxpayer Identification Number (ITIN)."

The 24 percent, and when it starts

The IRS runs backup withholding through two programs, and only one of them concerns a construction business:

BWH-B is the one that matters. It applies to payments reported on Forms 1099, and the IRS lists "independent contractor fees (1099-NEC)" explicitly among the payment types subject to it.

The practical sequence looks like this:

1. You pay a sub without a W-9 on file. You should have withheld 24 percent.
2. You file a 1099-NEC with a missing or wrong TIN.
3. The IRS sends you a B notice (CP2100 or CP2100A). Now you must solicit a corrected TIN from the payee — and start withholding if you do not get one.
4. You are liable for the amounts you should have withheld.

Step 4 is the reason this article exists. There is no version of this where the subcontractor pays your withholding for you.

What "correct TIN" means in practice

A W-9 that has been filled in is not the same thing as a W-9 that is right. The name and the number have to match what the IRS has on file — and the most common mismatch in construction is entirely predictable:

The sub writes the business name on the top line and gives you a personal SSN. For a single-member LLC that has not elected corporate treatment, the IRS generally expects the owner's name and the owner's TIN, not the LLC's trade name. A mismatch here produces a B notice a year later, when the job is long finished and the sub has moved on.

The fix is not clever. It is reading the W-9 when it arrives instead of filing it unread, and checking three fields against each other: name, federal tax classification, and TIN.

What a W-9 does not do

This is where good record-keeping quietly turns into a misclassification problem.

A signed W-9 in your file is a number. It is not a legal finding that the person is an independent contractor. The IRS is unusually direct about how that question is decided instead — three categories of evidence, covered in full in contractor or employee: three tests, one California carve-out:

• Behavioral control: "Does the company control or have the right to control what the worker does and how the worker does his or her job?"
• Financial control: whether "the business aspects of the worker's job [are] controlled by the payer" — how they are paid, who reimburses expenses, who supplies the tools.
• Type of relationship: written contracts, employee-type benefits, whether the work is a core business function.

And then the sentence that rules out every checklist ever sold to a contractor:

"There is no 'magic' or set number of factors that 'makes' the worker an employee or an independent contractor and no one factor stands alone in making this determination."

If the classification is genuinely unclear, either side can file Form SS-8 and ask the IRS to decide. Expect it to take at least six months.

A working procedure for a small construction business

Nothing here needs software to work. It needs a rule that is applied every time.

1. W-9 before the subcontract is countersigned. Same moment you collect the certificate of insurance and the license number. No W-9, no start date.
2. Read the three fields — name, classification, TIN — instead of filing it blind.
3. Store it for the life of the relationship plus your record-retention period, not just the calendar year. You will need it when a B notice arrives fourteen months later.
4. Refresh it when anything changes. New entity, new name, new number.
5. Track payments per payee as you go, not in January. The 1099 threshold is a running total across the year, and a sub you paid in March is easy to lose.
6. If no TIN arrives, withhold 24 percent and remit it. It is not a threat you make; it is a duty you have.

The one that catches everybody

You paid a sub $1,800 in April and $900 in October. In your head those are two small jobs. To the IRS they are one payee and one running total — and the reporting threshold changed for payments made after December 31, 2025 (see our article on the 1099-NEC). The W-9 you did not collect in April is the reason January is unpleasant.

Collect it in April.

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Current as of August 29, 2026. This article describes federal tax administration and is not tax or legal advice. Backup withholding rules, notice procedures and reporting thresholds are set by the IRS and change; the figures above are quoted from the IRS pages linked in the sources with the date they were checked.

What Zirko does: it keeps a record per business partner with the company data, contacts and the documents belonging to that relationship, so the W-9 sits next to the subcontract instead of in a mailbox. Zirko does not generate, transmit or validate IRS forms, does not run TIN matching, and does not calculate backup withholding. A document issued in Zirko is immutable — a correction is a separate document, so the payment history of a job stays readable after the fact.