Tax ID Number vs EIN vs Sales Tax ID: How to Tell Them Apart

Why these ID numbers get confused

“Tax ID number” is often used as a catch-all phrase, while “EIN” and “sales tax ID” refer to specific registrations. The confusion usually comes from:

• Different agencies issuing different IDs (IRS vs state revenue departments)
• Businesses needing multiple registrations at the same time (formation, payroll, sales tax, licensing)
• Forms and vendors asking for a “tax ID” without specifying which one

What “Tax ID Number” means (general definition)

A tax ID number is any identifying number used by a government tax authority to track a taxpayer. Depending on the context, “tax ID number” may refer to:

• EIN (Employer Identification Number) issued by the IRS for a business entity
• SSN (Social Security Number) used by a sole proprietor with no EIN
• ITIN (Individual Taxpayer Identification Number) for certain individuals who don’t qualify for an SSN
• State tax account numbers (varies by state) for payroll withholding, unemployment insurance, or other state-administered taxes
• Sales tax permit number (often called a sales tax ID) issued by a state for collecting/remitting sales tax

Common “tax ID” request scenarios

• Banking and payroll usually means EIN (or SSN for certain sole proprietors)
• Sales tax collection means a state sales tax permit/sales tax ID
• Vendor onboarding (W-9) usually means EIN or SSN (the taxpayer ID used for federal reporting)

What an EIN is (and what it’s used for)

An EIN is a nine-digit federal tax identification number issued by the IRS to identify a business entity for federal tax purposes.

Typical reasons a business needs an EIN

• Hiring employees and running payroll
• Operating as a corporation or partnership
• Opening many business bank accounts or obtaining business credit
• Filing certain federal tax returns (employment, excise, and some information returns)
• Separating business and personal tax identity (common for LLCs, even single-member LLCs)

What an EIN is not

• Not a sales tax permit
• Not proof you are registered to collect sales tax
• Not a state-issued account number

What a Sales Tax ID is (sales tax permit, seller’s permit, resale number)

A sales tax ID generally refers to a state-issued sales tax permit number (names vary by state). It authorizes a business to collect sales tax from customers and remit it to the state.

When you need a sales tax ID

• Selling taxable goods or services in a state that imposes sales tax
• Having sales tax nexus in a state (physical presence, economic thresholds, or marketplace rules)
• Making taxable retail sales, including online sales, where state rules require collection

Sales tax ID vs resale certificate

• Sales tax ID (permit): your registration with the state to collect/remit sales tax.
• Resale certificate: a document you provide to suppliers to buy inventory for resale without paying sales tax at purchase (when allowed). Many states tie resale privileges to having an active sales tax permit.

Key differences at a glance

Which one do you need? Practical decision guide

If you are starting a business

• Need an EIN if you will hire employees, operate as a partnership/corporation, or want a separate federal business identifier.
• Need a sales tax ID if you will sell taxable products/services in a state where you have nexus.

If you are filling out a W-9

• Use the taxpayer identification number tied to the name on the form:
  • Sole proprietor: often an SSN (or EIN if you use one for reporting)
  • LLC/partnership/corporation: typically an EIN
• A sales tax ID is generally not used for federal W-9 reporting.

If a vendor asks for your “tax ID”

• Ask what the ID will be used for:
  • 1099 reporting or payment setup: EIN/SSN
  • Tax-exempt purchase for resale: resale certificate (often supported by your sales tax permit)
  • State sales tax compliance: sales tax ID

State-specific example: Arizona (sales tax licensing)

States use different terms and processes for sales tax registration. Arizona, for example, uses transaction privilege tax (TPT) concepts that function similarly to sales tax collection requirements for many businesses. If you’re registering in Arizona, review the Arizona Sales Tax Number overview and the Arizona State Sales Use Tax Number Identification Application page for the information typically needed to apply and maintain the account.

Common mistakes to avoid

• Assuming an EIN allows sales tax collection (sales tax requires state registration)
• Using a sales tax ID on federal forms like W-9s or payroll filings
• Registering for sales tax without nexus (can trigger filing obligations even with no tax due)
• Failing to update registrations after entity changes, ownership changes, or address changes
• Mixing up multiple state account numbers (withholding, unemployment, sales tax) and using the wrong one on returns

FAQ: Tax ID Number vs EIN vs Sales Tax ID

1) Is an EIN the same thing as a tax ID number?

An EIN is a type of tax ID number. “Tax ID number” can also mean an SSN, ITIN, or a state-issued tax account number, depending on the situation.

2) Is a sales tax ID the same as an EIN?

No. An EIN is issued by the IRS for federal tax identification. A sales tax ID is issued by a state to authorize sales tax collection and to track sales tax filings and payments.

3) I’m a sole proprietor with no employees. Do I need an EIN?

Often, no. Many sole proprietors can use an SSN for federal tax reporting. You may still choose to get an EIN for banking, vendor onboarding, or privacy reasons, and you may still need a sales tax ID if you sell taxable items and have nexus.

4) Can I collect sales tax if I have an EIN but no sales tax permit?

Generally, no. Sales tax collection typically requires a state registration (sales tax permit). Collecting without the proper permit can create compliance and penalty issues.

5) What number goes on a W-9: EIN or sales tax ID?

W-9 forms use a federal taxpayer identification number (EIN or SSN, depending on the taxpayer/entity). A sales tax ID is not typically used for W-9 reporting.

6) If I sell online, do I automatically need a sales tax ID in every state?

No. Sales tax registration is generally driven by nexus rules, which can include physical presence, economic thresholds, and marketplace facilitator rules. You register where you have a registration obligation.

7) What’s the difference between a sales tax ID and a resale certificate?

A sales tax ID is your state account/permit to collect and remit sales tax. A resale certificate is a document used to buy goods for resale without paying sales tax at purchase (when allowed). Many states require