EIN Registration for Corporations (C-Corp and S-Corp)

Nov. 13, 2025, 7:16 p.m.
Every corporation operating in the United States—whether a C-Corporation (C-Corp) or an S-Corporation (S-Corp)—is required by the IRS to have an Employer Identification Number (EIN). This nine-digit number functions like a business’s Social Security Number and is used for tax filings, payroll, banking, and legal identification. Whether you’re forming a new corporation or converting an existing business, understanding how to register for an EIN is one of the first steps to staying compliant with federal and state tax laws.
EIN for Corporations

1. Why Corporations Need an EIN

Corporations are considered separate legal entities from their owners.
This means that all financial and tax activities must be tied to the corporation’s EIN—not the personal SSNs of the owners or shareholders.

You need an EIN to:

  • File federal and state corporate taxes

  • Open a business bank account

  • Hire employees and run payroll

  • Apply for business loans or credit

  • Register for state permits or licenses

2. C-Corp vs. S-Corp: EIN Requirements

Both C-Corps and S-Corps must have an EIN, but how the EIN is used can differ slightly depending on the business structure.

Type Tax Treatment EIN Use
C-Corporation Pays corporate income tax separately from owners. EIN used for corporate tax filing (Form 1120), payroll, and banking.
S-Corporation Passes income/losses to shareholders’ personal returns. EIN used for payroll, information returns, and Form 1120-S filing.

Tip: You must first obtain an EIN as a corporation before you can elect S-Corp status using IRS Form 2553.

3. Steps to Register for an EIN

You can register directly with the Internal Revenue Service (IRS) at no cost.
Here’s how:

Step 1: Form Your Corporation

  • File your Articles of Incorporation with your state’s Secretary of State.

  • Choose your corporate structure (C-Corp or S-Corp).

Step 2: Gather Required Information

You’ll need:

  • Legal business name (as filed with the state)

  • Principal business address

  • Responsible party’s name and SSN or ITIN

  • Type of business activity

  • Number of employees expected in the next 12 months

Step 3: Apply for an EIN

You can apply:

  • Online: https://www.fmcsa.me/

  • By Fax: Complete Form SS-4 and send to the IRS fax number

  • By Mail: Mail Form SS-4 to the IRS

  • By Phone: For international applicants only: +1-502-547-2551

Once approved, you’ll receive your EIN immediately (online) or within 4–6 weeks (mail or fax).

4. Electing S-Corporation Status

If you plan to operate as an S-Corporation, you must make a special election with the IRS.

After receiving your EIN:

  1. Complete Form 2553 (Election by a Small Business Corporation)

  2. File within 75 days of forming your corporation (or by March 15 for existing corporations)

  3. Wait for IRS confirmation of your S-Corp election

5. After You Receive Your EIN

Once your EIN is issued:

  • Use it for all tax filings and bank accounts

  • Register for state business taxes (income, sales, payroll, etc.)

  • Maintain accurate business records under your EIN

  • Never use your personal SSN for corporate purposes

Important: Your EIN is permanent and cannot be reused by another entity, even if your corporation closes.

6. Common EIN Mistakes to Avoid

  • Applying for an EIN before forming the corporation

  • Using an incorrect legal business name on Form SS-4

  • Forgetting to elect S-Corp status after EIN issuance

  • Submitting duplicate applications (can cause IRS delays)

  • Sharing the EIN across unrelated entities

7. Frequently Asked Questions

Q: Can I use the same EIN if my C-Corp converts to an S-Corp?
 Yes. The EIN remains the same because the business entity doesn’t change — only its tax classification.

Q: Can a single shareholder apply for an EIN for their S-Corp?
 Absolutely. Even single-shareholder corporations must have an EIN.

Q: What if I lose my EIN confirmation letter?
You can request a replacement by contacting the IRS Business & Specialty Tax Line: 1-800-829-4933.

8. Summary

Step Action Details
1 Form Corporation File Articles of Incorporation with your state
2 Apply for EIN Use IRS Form SS-4 or online portal
3 Elect S-Corp (if applicable) File IRS Form 2553
4 Maintain Compliance File taxes, payroll, and state registrations using EIN

Conclusion

Registering for an EIN is a simple but essential step in launching and maintaining your corporation’s legal and financial foundation.
Whether you operate as a C-Corp or S-Corp, your EIN ensures that your business can file taxes, open bank accounts, and stay compliant with both state and federal regulations.