If you're starting a US company, especially as a non-US citizen or first-time founder, three nine-digit numbers keep showing up: SSN, ITIN, and EIN. They sound similar, but they serve very different purposes, and using the wrong one can delay your bank account, payroll, or tax filings by weeks.
Here's what each tax ID is, when you need it, and how to get it.
ITIN vs. EIN vs. SSN at a glance
| Feature | SSN | ITIN | EIN |
|---|---|---|---|
| What it stands for | Social Security Number | Individual Taxpayer Identification Number | Employer Identification Number |
| Who gets it | US citizens and work-authorized residents | Non-resident aliens and others who can't get an SSN but need to file US taxes | Businesses, LLCs, corporations, trusts |
| Format | XXX-XX-XXXX | 9XX-XX-XXXX (always starts with 9) | XX-XXXXXXX |
| Issued by | Social Security Administration | IRS | IRS |
| Purpose | Personal tax ID and work authorization | Personal tax filing only. Does not authorize work | Business tax ID, payroll, banking |
| Can you work in the US with it? | Yes | Yes | Not applicable (it's for the business, not a person) |
| How to apply | Form SS-5 at any Social Security office | Form W-7 with tax return or a Certifying Acceptance Agent | Form SS-4, online at IRS.gov (fastest) |
| How long it takes | 2 to 4 weeks | 7 to 11 weeks | Immediate online (with SSN); 4 to 6 business days by fax |
| Cost | Free | Free | Free (avoid third-party sites that charge fees) |
An SSN (Social Security Number) is issued by the Social Security Administration exclusively to US citizens and work-authorized noncitizens. It's your personal tax identifier and authorizes employment.
An ITIN (Individual Taxpayer Identification Number) is assigned to an individual human who needs to file US taxes but isn't eligible for an SSN. Common examples: non-resident founders who receive US-source income, foreign owners of US LLCs, spouses and dependents of work-visa holders.
An EIN (Employer Identification Number) is assigned to a business entity: an LLC, C-corp, S-corp, partnership, or trust. The EIN identifies the business to the IRS for tax filings, hires employees, and opens business bank accounts. It has nothing to do with immigration status.
Quick test: if a form is asking "who owns this business?" you use the owner's SSN or ITIN. If it's asking "what is this business's tax ID?" you use the EIN.
EIN vs. SSN v ITIN: When to use which
Different startup activities require different identification numbers, and confusing them can create significant delays.
| Business Activity | Required Tax ID | Notes |
|---|---|---|
| Opening business bank account | EIN | SSN of 25%+ owners also typically required |
| Hiring W-2 employees | EIN | Plus state employer IDs where employees work |
| Filing business taxes | EIN | For LLCs, corporations, partnerships |
| Receiving payments as contractor | SSN or ITIN | Report on personal return |
| Issuing 1099s to contractors | EIN | Must have EIN to be a paying entity |
| Cap table/equity issuance | EIN | Shareholders need SSN or ITIN |
| 83(b) election filing | SSN or ITIN | Personal tax election for restricted stock |
| Filing personal tax return | SSN or ITIN | ITINs for those ineligible for SSN |
SSN, EIN, and ITIN are all nine-digit tax IDs issued by the US government, but they identify different things:
- Use your SSN when you're being paid personally, as an employee, as a sole proprietor without an EIN, or for personal tax filings.
- Use your business's EIN when anything involves the business entity: opening a business bank account, running payroll, issuing 1099s, filing corporate tax returns, applying for business credit.
- Use your ITIN for tax-filing purposes. It does not give you the right to work in the US, does not qualify you for Social Security benefits, and is not a form of identification for anything outside the IRS.
If you're on a work-authorized visa (H-1B, L-1, O-1, TN, etc.), you should apply for an SSN, not an ITIN. The SSN covers tax filing AND work authorization. Only apply for an ITIN if you genuinely cannot get an SSN.
A common founder mistake: using your SSN on W-9 forms that your clients send to your LLC. If the client is paying your business, they need the business's EIN. If you give them your SSN, the income shows up on your personal tax record instead of the business's, which can create a mess at tax time and undermine the liability protection of your LLC.
As soon as you form an LLC or corporation, get an EIN and use it everywhere in place of your SSN for business purposes.
Guidance for non-US citizen founders by visa type
Your immigration status determines whether you qualify for an SSN, which in turn affects your application process and timeline.
Work-authorized visas qualify for SSN
H-1B visa holders are immediately eligible for an SSN upon work authorization. Under 2024 DHS rules, startup founders can self-sponsor H-1B through their own company if they establish an employer-employee relationship (board of directors recommended) and can pay prevailing wage.
O-1 visa holders (extraordinary ability) have the most favorable status for founders with no wage requirement, no annual cap, unlimited extensions, and self-sponsorship through an agent is permitted. Apply for SSN at any Social Security office with your passport, I-94, and O-1 approval notice.
E-2 treaty investors receive work authorization incident to status and can apply for SSN immediately upon US entry. Notably, E-2 spouses are also work-authorized and SSN-eligible, though children are not.
L-1 visa holders (intracompany transferees) are automatically SSN-eligible, as are L-2 spouses since January 2022.
F-1 students on OPT can obtain SSNs but only with authorized employment. Self-employment on OPT is permitted if the business relates to your field of study, but STEM OPT extension cannot be used with a sole proprietorship (you cannot be your own employer), and CPT does not allow self-employment.
Non-work-authorized visas require ITIN
B-1/B-2 visitors are not eligible for SSN and must use ITIN for any US tax filing obligations. Critically, B-1/B-2 holders can legally incorporate a US company and obtain an EIN but cannot work for that company or draw salary. This creates a viable path for international founders to establish their US entity while pursuing an appropriate visa.
For non-work-authorized founders, the optimal sequence is: form your business entity, apply for EIN by fax (writing "Foreign" where SSN/ITIN is requested), then apply for ITIN when you have a US tax filing obligation.
Common mistakes international founders make
The most frequent error is applying for ITIN when eligible for SSN. You should always apply for SSN first if you have work authorization. Other common mistakes include submitting expired documents, name mismatches between documents, using photocopies instead of originals, and applying for EIN before incorporating the business entity.
For EIN applications, listing a company as responsible party (must be an individual), using incorrect SSN/ITIN format, and omitting return fax numbers all cause delays. Non-US founders should use a US registered agent address and ensure Form SS-4 is signed by the responsible party.
What to do if you’re a first-time founder
The optimal sequence for all founders is:
- Incorporate your entity with the state (Delaware most common, 1-2 business days)
- Apply for EIN (instant online with SSN, or 4+ days by fax without)
- File 83(b) election within 30 days of receiving restricted stock
- Open business bank account (1-2 days once EIN received)
- Register for state tax IDs when ready to hire employees
Attempting to get an EIN before incorporation will fail because the IRS requires your entity to exist first. Similarly, most banks require EIN documentation before opening business accounts.
Bank account requirements vary by institution
Most startup-friendly banks require your company's EIN plus personal identification from beneficial owners. Mercury requires Articles of Incorporation, IRS-issued EIN document, government ID for each 25%+ owner, and a physical business address (not PO Box or registered agent). Brex requires VC funding or $1M+ revenue or $500K+ cash balance to qualify. Traditional banks like Chase often require in-person branch visits.
For non-US founders, Mercury and similar fintechs accept applications with EIN and passport, making them the primary banking option for international entrepreneurs. Expect 1-2 weeks for account approval after EIN receipt if applying from outside the US.
Payroll requires EIN plus state registrations
Before running payroll, you need your federal EIN plus state employer identification numbers in every state where employees work. State registrations typically take 1-12 weeks depending on jurisdiction. Payroll providers like Warp, Gusto, and Rippling can assist with state registrations through their onboarding process.
For 1099 contractors, collect Form W-9 before any payment. If a contractor doesn't provide a W-9, you must withhold 24% backup withholding. International contractors require Form W-8BEN and may be subject to 30% withholding unless a tax treaty applies.
The 83(b) election deadline is absolute
Perhaps the most critical deadline for founders receiving restricted stock is the 83(b) election, which must be filed within 30 days of your stock grant. No extensions are permitted. This election lets you pay taxes at grant (when shares are worth pennies) rather than at vesting (when they may be worth dollars). Missing this deadline can result in massive unexpected tax bills years later.
The election requires your SSN or ITIN and your company's EIN. Starting July 2025, the IRS accepts electronic filing, though certified mail remains the traditional approach.
Delaware franchise tax and ongoing compliance
Delaware corporations must file an annual report and pay franchise tax by March 1 each year. Using the Assumed Par Value method, most startups pay the $400 minimum plus a $50 filing fee. The default Authorized Shares method can produce shockingly high calculated taxes for companies with many authorized shares. Make sure you always calculate both methods and pay the lower amount. Late filing incurs a $200 penalty plus 1.5% monthly interest.
Delaware LLCs and LPs pay a flat $300 annual tax due June 1, with no annual report required. The late penalty structure mirrors corporations.
Several states have decoupled from OBBBA provisions due to revenue concerns, including California, Rhode Island, Michigan, Pennsylvania, and Delaware itself. This creates compliance complexity for startups operating in multiple states where state tax treatment may differ significantly from federal treatment for provisions like R&D expensing and bonus depreciation.
Need help with payroll setup after you've got your EIN? Warp automates multi-state compliance and state tax registrations for venture-backed startups, so you can focus on building your company instead of navigating tax bureaucracy.
Frequently asked questions
Can I get an EIN without an SSN or ITIN?
Yes. Non-US founders can apply for an EIN by faxing or mailing Form SS-4 with "Foreign" entered on line 7b. Fax processing takes approximately 4 business days. You do not need an SSN or ITIN to obtain an EIN for your business.
Is EIN the same as TIN?
An EIN is a type of TIN. TIN (Taxpayer Identification Number) is an umbrella term the IRS uses for any tax ID. It includes SSNs, ITINs, EINs, and a few others. So every EIN is a TIN, but not every TIN is an EIN.
What's the difference between SSN and ITIN?
An SSN is issued to US citizens and work-authorized noncitizens—it both identifies you for tax purposes and authorizes employment. An ITIN is issued to individuals with US tax obligations who are not eligible for an SSN—it is only for tax purposes and does not authorize work.
How long does it take to get a tax ID?
SSNs take approximately 14 days after applying in person. ITINs take 7-11 weeks standard (up to 15 weeks during tax season). EINs are instant online with SSN/ITIN, 4 business days by fax, or 4-8 weeks by mail.
Do I need an EIN if I'm a sole proprietor with no employees?
Not always—you can use your SSN for tax purposes. However, getting an EIN is recommended to avoid giving out your SSN on W-9 forms and invoices, and you'll need one if you ever hire employees or open a business bank account.
Can I incorporate a US company on a tourist visa?
Yes. B-1/B-2 visitors can legally form and own US companies. However, you cannot work for or draw salary from that company without work authorization. Many international founders incorporate and obtain EINs while on tourist visas, then pursue appropriate work visas to actively operate the business.
Can someone undocumented get an ITIN or EIN?
Yes to both, in most cases. The IRS issues ITINs and EINs based on tax obligations, not immigration status. An undocumented individual who has US-source income can apply for an ITIN (Form W-7) to file taxes. An undocumented individual who owns a US business can apply for an EIN for that business (Form SS-4). Neither provides work authorization.
