How to Fill Out a W-9: Step-by-Step Guide

If you do any independent contracting, freelance work, or vendor sales, a client will eventually email you a blank Form W-9 and ask you to "fill it out and send it back." The form is short, one page, but the boxes trip people up, and a small mistake can trigger 24% backup withholding or a name mismatch notice from the IRS months later.

This guide walks through the current W-9 line by line, explains the parts that actually cause problems (tax classification and TINs), and shows you how to return the form without handing your Social Security number to strangers.

What a W-9 Is For

Form W-9, Request for Taxpayer Identification Number and Certification, does one job: it gives the business paying you the information they need to report that payment to the IRS. When a company pays a non-employee $600 or more in a year for services, it has to file a Form 1099-NEC reporting the total. To do that, it needs your legal name and taxpayer identification number (TIN). The W-9 is how you hand those over.

You are not filing anything with the IRS when you complete a W-9. You give it to the requester, the client or company that asked for it. They keep it in their records and use it at tax time. That distinction matters, because a common panic is people trying to mail the form to an IRS address. Don't.

W-9s also show up outside contractor work: banks request them when you open an interest-bearing account, brokerages use them for dividend reporting, and they appear in real estate transactions, debt cancellations, and IRA contributions. The line-by-line process is the same regardless of why someone asked.

Make sure you are working from the current version. The IRS released a revised W-9 in March 2024, and it added a new line (3b) for certain pass-through entities. Download a fresh copy from IRS.gov rather than reusing an old PDF, or fill out the substitute W-9 your client provides.

Before You Start: SSN or EIN?

The one decision to make before touching the form is which taxpayer identification number you will use.

• Individuals and sole proprietors can use a Social Security number (SSN). You can also apply for an Employer Identification Number (EIN) and use that instead, even with no employees.
• Single-member LLCs treated as disregarded entities use the owner's SSN or EIN.
• Multi-member LLCs, partnerships, and corporations must use an EIN.

If you are a sole proprietor, getting an EIN is worth the ten minutes it takes. It keeps your Social Security number off paperwork that circulates through client accounting departments, which is a real identity-theft reduction. Our walkthrough on how to get a federal tax ID covers the free IRS application. Whichever number you pick, it has to match the name you put on line 1, so decide now.

How to Fill Out a W-9, Step by Step

The form has two areas: an information section at the top and a certification at the bottom. Here is what goes in each box.

Step 1: Line 1, Your Name

Enter your name exactly as it appears on your income tax return. For an individual or sole proprietor, that is your personal legal name, not your business name. This line can never be left blank. If your legal name changed recently, say after marriage, and you haven't updated it with the Social Security Administration yet, use the name currently on file with the SSA to avoid a mismatch.

Step 2: Line 2, Business or Disregarded Entity Name

Fill this in only if you operate under a business name, DBA, or disregarded-entity name that differs from line 1. A freelance designer working as "Jane Smith" leaves it blank; someone doing business as "Bright Studio" would put that here while keeping their personal name on line 1.

Step 3: Line 3a, Federal Tax Classification

Check one box describing how you are taxed:

• Individual/sole proprietor or single-member LLC, which covers most freelancers and one-person businesses.
• C corporation or S corporation, if you incorporated and made that election.
• Partnership, for multi-member arrangements taxed as a partnership.
• Trust/estate.
• Limited liability company. Check this box and enter a letter for how the LLC is taxed: C, S, or P.

This line causes more errors than any other, especially for LLC owners, which the next section covers on its own.

Step 4: Line 3b, Pass-Through Entities With Foreign Owners

This checkbox is new to the 2024 revision and applies to a narrow group: partnerships, trusts, and estates that are themselves providing the W-9 to a flow-through entity and that have foreign partners, owners, or beneficiaries. If you are an individual, a sole proprietor, or a standard domestic LLC, you skip it. Most contractors will never touch line 3b.

Step 5: Line 4, Exemption Codes

Line 4 has two fields: an exempt payee code and a FATCA exemption code. These apply mainly to corporations, tax-exempt organizations, and certain financial entities that are exempt from backup withholding or FATCA reporting. Individuals and ordinary sole proprietors leave both blank. If a code applies to your entity type, the W-9 instructions list them by number.

Step 6: Lines 5 and 6, Address

Enter the mailing address where the requester should send your 1099. Use an address you will still have access to next January, because that is when the forms go out. Line 5 is the street; line 6 is city, state, and ZIP.

Step 7: Line 7, Account Numbers (Optional)

If the requester asked you to reference a specific account or vendor number, put it here. Otherwise leave it empty.

Step 8: Part I, Taxpayer Identification Number

Enter the SSN or EIN you settled on earlier. Sole proprietors put their SSN in the SSN boxes or their EIN in the EIN boxes, not both. Double-check the digits against your Social Security card or IRS EIN letter. A single transposed number here is what produces a name/TIN mismatch later.

Step 9: Part II, Certification

Sign and date the form. By signing, you certify under penalty of perjury that the TIN is correct, that you are a U.S. person, and that you are not subject to backup withholding, unless the IRS has notified you otherwise. If you have received an IRS notice telling you that you are subject to backup withholding for underreported interest or dividends, you must cross out the second certification item before signing. Almost no one is in that situation, but read the certification so you know what you are attesting to.

The LLC Trap on Line 3a

Line 3a snares LLC owners constantly, so it deserves its own treatment.

If you own a single-member LLC that has not elected to be taxed as a corporation, the IRS treats it as a disregarded entity. Counterintuitively, you do not check the "Limited liability company" box. You check "Individual/sole proprietor or single-member LLC," put your own name on line 1, and put the LLC's name on line 2. The TIN is your SSN or the owner's EIN.

You only check the "Limited liability company" box, and enter C, S, or P, when the LLC has multiple members or has elected corporate taxation. A two-person LLC taxed as a partnership enters "P"; an LLC that filed to be an S corp enters "S."

Getting this wrong does more than annoy your client's bookkeeper. If the name and TIN combination doesn't match IRS records, the agency sends the payer a CP2100 or "B" notice, and the payer may be required to start backup withholding on your future payments until you fix it. Before you decide how to structure the relationship in the first place, it helps to understand the classification rules, which our guide on 1099 vs. W-2: choosing between a contractor and an employee walks through in plain terms.

Backup Withholding: What's Actually at Stake

The whole certification exists because of backup withholding. When a payer does not have a correct, signed W-9, or the IRS has flagged your account, the payer must withhold 24% of your payments and send it to the IRS on your behalf.

That is not a penalty in the sense of money you lose permanently; you get credit for it when you file your return. But it is a cash-flow hit. Withhold 24% from every invoice for a year and you are effectively giving the government an interest-free loan until spring. A correctly completed W-9 with a matching name and TIN is all it takes to avoid it, which is why the two minutes spent double-checking Part I pays off.

Common Mistakes to Avoid

• Sending it to the IRS. The W-9 goes to the requester. Only the year-end 1099 goes to the IRS, and the payer files that, not you.
• Name and TIN mismatch. The single most common cause of backup-withholding notices. Confirm line 1 and Part I agree with your Social Security card or EIN letter.
• The wrong LLC classification. Single-member LLCs check the individual box, not the LLC box. Review the section above if you are unsure.
• Emailing it unencrypted. A W-9 usually contains a Social Security number. Plain email is the last way you want to send that. Use an encrypted portal, a password-protected PDF, or the client's secure upload link.
• Leaving the certification unsigned. An unsigned W-9 is incomplete, and many payers will treat it as no W-9 at all and start withholding.
• Using a W-9 as a foreign person. Non-U.S. individuals and entities use the W-8 series (usually W-8BEN), not the W-9. Signing a W-9 while certifying you are a U.S. person when you are not is a false certification.

How to Return Your W-9 Safely

Because the form carries your TIN, treat it like the sensitive document it is. Prefer, in order: a secure client upload portal, an encrypted file-sharing link, or a password-protected PDF where you send the password through a separate channel. Avoid attaching an unprotected W-9 to a regular email or posting it in a shared drive that other vendors can see.

Keep a copy of what you submitted, along with the date. If a client later claims they never received it and threatens backup withholding, your record settles it quickly. If you work with many clients, a single up-to-date PDF you can re-send saves you from re-keying the same information every time one asks.

Where the W-9 Fits in Your Contractor Paperwork

The W-9 is one piece of a clean contractor setup. It handles tax reporting, but it says nothing about scope, payment terms, ownership of your work, or confidentiality. Those belong in a written agreement signed before the work starts. If you are the one hiring, our guide to hiring 1099 contractors and staying IRS-compliant covers collecting W-9s alongside proper classification. If you are the contractor, pairing your W-9 with a solid independent contractor agreement protects the parts a tax form never touches.

Collect the W-9 up front, before the first payment, so you are not chasing a signature in January when 1099s are due. Treat it as part of onboarding, right next to the signed contract.

Generate Your Independent Contractor Agreement with Contractable

A W-9 handles the IRS side of a contractor relationship, but the terms that actually protect you, scope, payment schedule, IP ownership, and confidentiality, live in the contract. Contractable generates a customized independent contractor agreement in seconds, so you can pair it with your W-9 and start the engagement on solid footing. No lawyers or legal jargon required.