Getting a tax ID is often the first practical step for businesses, nonprofits, and individuals handling specific income situations. The process is straightforward when you know which identifier you need and which agency issues it.
This guide walks you through the most common paths, explains when you must apply in person, and highlights documentation that prevents delays. Use it as a checklist before you contact the relevant government office.
| Identifier | Issuing Agency | Primary Use | When Required |
|---|---|---|---|
| EIN (Employer Identification Number) | IRS | Hiring employees, opening business bank accounts, filing tax returns | Multi-member LLCs, corporations, nonprofits with employees |
| ITIN (Individual Taxpayer Identification Number) | IRS | File taxes for nonresident or undocumented aliens without SSN | Nonresidents, dependents or spouses of U.S. citizens without SSN |
| SSN (Social Security Number) | SSA | Personal income reporting, employment, government benefits | Sole proprietors without employees, some trustors |
| State Tax ID | State Department of Revenue | State-level filing, withholding registration, sales tax permit | Businesses registered or operating in a particular state |
How to Apply for an EIN Online or by Mail
An Employer Identification Number is the most common federal tax ID for businesses. You can apply on the IRS website in minutes or submit Form SS-4 by mail if online access is unavailable.
The online system provides immediate confirmation, while mailed applications take several weeks. Make sure the person listed on the form has authority to act on behalf of the entity.
Once you receive the number, store it securely and use it exactly as shown when opening bank accounts, filing returns, or hiring staff.
Applying for an ITIN When You Do Not Qualify for SSN
If you or a dependent need to file U.S. taxes but are not eligible for a Social Security Number, an ITIN is required. This includes nonresident aliens, their spouses, and dependents who cannot obtain an SSN.
Complete Form W-7 with original or certified foreign identity documents. You may submit with a valid tax return or choose a standalone submission if you need only the ITIN.
Review current instructions carefully, as document acceptance rules and acceptance centers change periodically. Using a certified acceptance agent can simplify in-person reviews.
Using Your Personal Social Security Number as a Tax ID
For sole proprietors without employees, the owner’s Social Security Number often serves as the federal tax ID on filings and banking documents. This avoids the need for a separate EIN unless you plan to hire staff or elect corporate status.
If you prefer privacy or anticipate hiring employees, consider applying for an EIN even as a single-member entity. It separates business identifiers from personal records and streamlines bank processes.
Clearly indicate on forms whether you are using an SSN or an EIN to avoid processing errors with the IRS or state agencies.
Registering for a State Tax ID and Permits
Many states require a separate state tax ID to report income, collect sales tax, or withhold payroll taxes. Check your state’s department of revenue website for specific thresholds and registration steps.
Some local jurisdictions also require additional permits or seller’s permits tied to a state-level ID. Keep a record of state registrations alongside your federal identification for audits or inquiries.
Renewal rules vary, so note expiration dates and set reminders before they lapse, especially if your registration status changes due to ownership or structure changes.
Document Checklist and Submission Tips
Gathering strong supporting documents reduces delays and questions from processing centers.
- Completed application form (SS-4 for EIN, W-7 for ITIN, or state equivalent)
- Proof of entity structure or identity (articles of organization, birth certificate, or passport)
- Authorization letter signed by the responsible party
- Tax return or other supporting documents when required
- Payment method for applicable fees, if applicable
Key Steps to Secure and Use Your Tax Identification
Treat your tax ID like other important legal numbers by limiting access, storing physical documents safely, and reviewing records annually. Establishing clean processes early prevents complications during audits, audits, or business transitions.
- Confirm which identifier the specific agency or bank requires before submitting forms
- Complete applications with consistent names and accurate entity details
- Keep copies of submissions, receipts, and confirmation numbers
- Update records promptly if ownership, address, or entity structure changes
- Verify expiration or renewal rules for state and federal identifiers
FAQ
Reader questions
Can a small business owner without employees use their SSN instead of an EIN?
Yes, sole proprietors without employees may use their Social Security Number on tax filings and bank accounts, though switching to an EIN is recommended for privacy and future hiring.
How long does it take to receive an ITIN after submitting Form W-7?
Processing times vary, but most applicants receive their ITIN within seven to ten weeks when submitting a complete application with proper documentation by mail.
If my business structure changes from sole proprietorship to LLC, do I need a new EIN?
Generally, an LLC must apply for a new EIN with the IRS when it is formed, even if the owner previously used their SSN or had an EIN for a prior business.
What should I do if my state tax ID was lost or stolen?
Contact your state’s department of revenue immediately to report the loss and request a replacement ID; follow their specific verification steps before reusing the number on filings.