A new client will send you a W-9 and ask for your taxpayer identification number. Your bank will request your EIN when opening a new account. One state’s registration application is asking for your FEIN. And then it occurs to you that maybe there is a difference between those numbers, and that you might have been providing the wrong detail.
In most cases, there is only one number you need. The IRS refers to any number that identifies a taxpayer as a TIN (taxpayer identification number). A business or entity’s specific taxpayer number is an EIN (employer identification number). Every EIN is a TIN, but every TIN is not an EIN. When a form requests a TIN, it will be whatever number identification applies to the taxpayer filing the form.
The problem is having the wrong number on the wrong form comes due later as mismatched information on a 1099 tax form or an IRS notice. Having the wrong TIN on file can also lead to additional backup withholding being taken out of payments that should have been issued tax-free.
The TIN problem I run into most when onboarding a new client isn't dramatic. It's a vendor file where half the contractors never returned a W-9, a few gave an SSN when their LLC has its own EIN, and one name doesn't match the number at all.
None of it gets noticed until the 1099s go out and the IRS sends a CP2100 notice listing the mismatches, and by then the business is chasing people it stopped working with months ago. Collecting a W-9 before the first payment, and checking the name and number against IRS records, fixes nearly all of it.
Anu Gupta, CA, EA, B.Tech · LinkedInTIN vs EIN: The Core Relationship
TIN (Taxpayer Identification Number) is an UMBRELLA TERM used by the IRS for any number used to identify a taxpayer for tax purposes. An EIN is one specific type of TIN. There are four main types of TIN:
| TIN Type | Full Name | Who Uses It | Format |
|---|---|---|---|
| SSN | Social Security Number | Individual US citizens and authorised residents | XXX-XX-XXXX |
| EIN | Employer Identification Number | Business entities (LLCs, corporations, partnerships, trusts, non-profits) | XX-XXXXXXX |
| ITIN | Individual Taxpayer Identification Number | Foreign individuals with US tax obligations who cannot get an SSN | 9XX-XX-XXXX (starts with 9) |
| ATIN | Adoption Taxpayer Identification Number | Adoptive parents claiming a child during pending adoption | 9XX-XX-XXXX (temporary) |
EIN Explained
An EIN identifies a business entity with the IRS, the business equivalent of an individual's SSN. Key uses:
- Filing business tax returns (Form 1120, 1065, 1120-S)
- Setting up payroll and filing payroll taxes (Form 941, W-2s)
- Opening a business bank account (banks require EIN)
- Issuing 1099 forms to contractors (you report your EIN as the payer's TIN)
- Filing Form W-9 when clients request your tax information
EINs are free and can be obtained instantly online at IRS.gov via Form SS-4.
When You See 'TIN' on a Form
When a form asks for a TIN, it is asking for whichever tax ID number is appropriate for the taxpayer:
- Individual filing personally: provide your SSN (or ITIN if you do not have an SSN)
- Business entity (LLC, corporation, partnership): provide your EIN
- Sole proprietor with no EIN: may provide SSN, but using an EIN is recommended to protect your SSN
The W-9 (Request for Taxpayer Identification Number) is the most common form where this comes up. Vendors and contractors complete a W-9 to provide their TIN (SSN or EIN) to the business that will pay them, so that 1099s can be filed accurately.
Which SSN or EIN Number Goes on the Form
When a form asks for a TIN, give the number that belongs to the taxpayer the form is about:
- An individual filing personally: your SSN, or your ITIN if you aren't eligible for an SSN.
- A corporation, partnership, or multi-member LLC: the entity's EIN.
- A single-member LLC taxed as a disregarded entity: usually the owner's SSN or EIN on a W-9, not the LLC's own EIN, unless the LLC has elected corporate tax treatment. The W-9 instructions explain this in detail.
- A sole proprietor: either your SSN or your business EIN, if you have one.
The W-9 is where most of this comes up. It's how a contractor or vendor gives their TIN to the business paying them, so that business can file an accurate 1099. When the name and number on the W-9 don't match IRS records, the payer can be required to start backup withholding on future payments.
Should a Sole Proprietor Use an SSN or an EIN?
A sole proprietor with no employees and no retirement plan or excise tax obligations doesn't need an EIN. The SSN works for filing and on W-9s. Many still get an EIN because a W-9 gets passed around: it's emailed, saved in vendor systems, and kept by clients for years. An EIN keeps your personal Social Security number out of those files.
An EIN doesn't change how a sole proprietor is taxed. Income still goes on Schedule C of your personal return. The number only changes what appears on business paperwork.
We received an IRS notice because the TIN on one of our 1099s didn't match the IRS records, and we also realized we were missing W-9s for several vendors. Profitjets reviewed our vendor records, identified the mismatches, collected the missing documentation, and corrected the affected 1099 filings. What had started as one IRS notice turned into a full cleanup of our vendor tax records.
Approximately 40% of new Profitjets clients have at least one incomplete or mismatched vendor W-9 record at onboarding. Profitjets files more than 3,500 Forms 1099 annually for clients, including corrections for TIN mismatches and other reporting errors.
Book a free consultation and we will sort your registrations out.
FAQs
Is a FEIN the same as an EIN?
Yes. FEIN stands for Federal Employer Identification Number, and it's the same number as an EIN. People add "Federal" to tell it apart from state tax ID numbers, which states issue separately for things like state payroll or sales tax. The IRS itself just calls it an EIN.
Do I need a new EIN if I change my business structure?
Sometimes. A sole proprietor who incorporates or takes on partners needs a new EIN, and so does a partnership that converts to a corporation. Making an S-Corp election doesn't require a new one, because the election changes how an existing entity is taxed, not the entity itself. The IRS publishes a list of which changes need a new number, so check it before filing anything.
What happens if a 1099 has the wrong TIN?
The IRS matches each 1099 against its records. When the name and TIN don't match, the payer receives a notice listing the mismatches, often called a B-notice, and has to contact the payee for a corrected W-9. If the problem isn't fixed, the payer may have to withhold a portion of future payments as backup withholding, and penalties can apply for filing incorrect information returns.
Can I check whether a vendor's TIN is correct?
Yes. Businesses that file 1099s can use the IRS TIN Matching program through the IRS e-Services portal to confirm a name and TIN combination before filing. Running new vendors through it when you onboard them is much easier than sorting out mismatches after the notices arrive.
Is my EIN confidential?
Not the way an SSN is. A business EIN routinely appears on invoices, W-9s, 1099s, and public filings for some organisations, such as nonprofits. It still makes sense to share it only when there's a reason, since it can be misused to open accounts or file fraudulent returns in the business's name.
Written by
Anu Gupta, CA, EA, B.Tech
Anu works with US businesses on tax and entity questions at Profitjets, from choosing a structure to the filings that follow it. She writes about the decisions owners make once and then live with for years. Connect on LinkedIn
Free consultation
Unsure Which Number to Give?
Book a free consultation and we will sort your registrations out.