TIN, SSN, or EIN — Which Goes on Your W-9?

The acronyms, defined

• TIN — Taxpayer Identification Number. The umbrella term. Any of the IDs below qualifies as a TIN.
• SSN — Social Security Number. Your personal 9-digit number assigned at birth or when you became a U.S. resident. Format: XXX-XX-XXXX.
• EIN — Employer Identification Number. A 9-digit number assigned to businesses by the IRS. Format: XX-XXXXXXX.
• ITIN — Individual Taxpayer Identification Number. For individuals who can't get an SSN (typically non-resident aliens). Format: 9XX-XX-XXXX (always starts with 9).

Which to use on your W-9 — the simple flowchart

You're an individual or sole proprietor → SSN

If you're freelancing under your personal name with no formal business entity, use your SSN. The IRS treats you and your business as the same taxpayer.

You're a single-member LLC → either SSN or EIN

This is the gray area. Single-member LLCs are "disregarded entities" by default — the IRS treats you the same as a sole proprietor for tax purposes. You can use either:

• Your SSN — IRS officially recommends this for disregarded entities
• Your EIN — perfectly acceptable, and many freelancers prefer this for privacy reasons (you don't have to give your SSN to clients)

If you've elected to be taxed as an S-corp or C-corp, you MUST use the EIN.

You're a multi-member LLC, partnership, or corporation → EIN

Any business entity with multiple owners or one that's incorporated must use its EIN. The entity has its own tax identity separate from any individual owner.

You're a non-resident alien with U.S. income → ITIN

If you're not a U.S. citizen and aren't eligible for an SSN, but you have U.S.-source income that needs reporting, you'd use an ITIN. (Foreign persons and entities usually file W-8 instead of W-9 — see our W-8 guide.)

Why people get an EIN even when they don't need one

Many sole proprietors and single-member LLC owners get an EIN even though they could legally use their SSN. Reasons:

• Privacy. You can give clients an EIN without exposing your SSN.
• Identity theft protection. EIN exposure is much less damaging than SSN exposure.
• Professionalism. Having an EIN signals you're operating as a business, not just moonlighting.
• Banking. Most business bank accounts require an EIN.
• Hiring employees. If you ever hire even one employee, you'll need an EIN anyway.

EINs are free from the IRS. You can apply online at IRS.gov and get your number in about 10 minutes. Don't pay third-party services that charge for this — they're just routing your application through the same free IRS portal.

Don't put both

The W-9 has two boxes — one for SSN, one for EIN. Use only one. Putting both creates confusion and may trigger IRS matching errors. Pick the one that fits your situation and leave the other blank.

What if your number changes?

If you switch from sole prop to LLC, get an EIN for the first time, or change business structures, send updated W-9s to all your clients with the new TIN. Don't wait for them to ask. Mismatched information between your W-9 and what's on file with the IRS triggers backup withholding.