How to Get an EIN in Connecticut (2026)

Fact-checked by the LegalGlass editorial team against primary sources · Published Aug 6, 2026 · Last updated Aug 6, 2026

To get an Employer Identification Number (EIN) for your Connecticut business, apply online directly through the IRS website. This method is free and typically results in immediate issuance of the EIN upon completion of the application. The EIN is a federal tax ID used for various business activities, including opening bank accounts and filing federal taxes.

What is an EIN?

The requirement for an EIN stems from federal tax law, specifically 26 U.S. Code § 6109, which mandates that any person required to make a return, statement, or other document must include an identifying number. For businesses, this identifying number is the EIN. While some sole proprietorships or single-member LLCs may operate using the owner's SSN, an EIN is generally necessary for most formal business structures and activities.

Who Needs an EIN in Connecticut?

Most businesses operating in Connecticut will need an EIN. The IRS specifies several situations that require an EIN:

• If you have employees.
• If your business is structured as a corporation or partnership.
• If you file any of these tax returns: Employment, Excise, or Alcohol, Tobacco, and Firearms.
• If you withhold taxes on income, other than wages, paid to a non-resident alien.
• If you have a Keogh plan.
• If you are involved with certain types of organizations, such as trusts (except certain grantor trusts), IRAs, exempt organizations, farmers' cooperatives, or real estate mortgage investment conduits (REMICs).

For Limited Liability Companies (LLCs) in Connecticut, the need for an EIN depends on their tax classification:

• Single-member LLCs: If a single-member LLC is treated as a disregarded entity (meaning its income and expenses are reported on the owner's personal tax return, Form 1040, Schedule C, E, or F), it generally does not need an EIN unless it has employees or elects to be taxed as a corporation. Otherwise, it can use the owner's SSN.
• Multi-member LLCs: All multi-member LLCs are treated as partnerships by default for federal tax purposes and must obtain an EIN.
• LLCs electing corporate taxation: Any LLC (single-member or multi-member) that elects to be taxed as a corporation (either C-corporation or S-corporation) must obtain an EIN.

Even if not strictly required by the IRS, many banks will require an EIN to open a business bank account, and some vendors or clients may request it for their records. Therefore, obtaining an EIN is a common and often practical step for nearly all Connecticut businesses, regardless of legal structure.

How to Apply for an EIN (Steps)

The process of applying for an EIN is free and can be completed through several methods, with the online application being the fastest. The IRS provides detailed instructions on how to apply.

1. Determine Eligibility: Ensure you are eligible to apply. The applicant must have a valid Taxpayer Identification Number (TIN), which can be a Social Security Number (SSN), an Individual Taxpayer Identification Number (ITIN), or an existing EIN. The "responsible party" is the individual or entity that ultimately owns or controls the entity or has sufficient control over the entity to direct or cause the direction of the management and policies of the entity.
2. Gather Required Information: Before starting the application, collect the following details:
   • Legal name of the business entity.
   • Trade name (DBA), if applicable.
   • Mailing address and physical address of the business.
   • Type of entity (e.g., sole proprietorship, partnership, corporation, LLC).
   • Reason for applying (e.g., started a new business, hired employees, changed organizational type).
   • Name and TIN (SSN, ITIN, or EIN) of the responsible party.
   • Number of employees expected in the next 12 months (if applicable).
   • Principal business activity.
3. Choose an Application Method:
   • Online (Recommended): The IRS online EIN application is the quickest method. It is available during specific hours (Monday to Friday, 7 a.m. to 10 p.m. Eastern Time). The EIN is typically issued immediately upon successful completion of the application. This method is generally only available to applicants with a legal residence or principal place of business in the United States or U.S. territories.
   • Fax: You can fax a completed Form SS-4, Application for Employer Identification Number, to the IRS. If you provide a fax number, the IRS will fax the EIN back within approximately four business days.
   • Mail: Mail a completed Form SS-4 to the IRS. This is the slowest method, taking several weeks to process and receive the EIN by mail.
   • Telephone (International Applicants Only): International applicants who do not have a legal residence or principal place of business in the U.S. may call the IRS at 267-941-1099 (not toll-free) to obtain an EIN. This service is available Monday to Friday, 6 a.m. to 11 p.m. Eastern Time.
4. Receive Your EIN: Once your application is processed, the IRS will issue your EIN. For online applications, it's immediate. For other methods, it will be sent via fax or mail. Keep this number in a safe place, as it is a permanent identification number for your business.

It is important to note that you can only apply for one EIN per responsible party per day. If you need more than one EIN for different entities, you must apply on separate days or use different responsible parties.

The Responsible Party Requirement

When applying for an EIN, the IRS requires the identification of a "responsible party." This individual or entity is the one who ultimately owns or controls the entity or has sufficient control over the entity to direct or cause the direction of the management and policies of the entity. The responsible party must have a valid Taxpayer Identification Number (TIN), which can be an SSN, ITIN, or an existing EIN.

• For a sole proprietorship, the responsible party is typically the sole proprietor.
• For a partnership, it is generally one of the partners.
• For a corporation, it is usually the principal officer.
• For an LLC, it depends on the structure: for a single-member LLC, it's the owner; for a multi-member LLC, it's typically one of the members.

The responsible party's information is used for identification purposes and does not necessarily mean they are personally liable for the business's debts or taxes, especially if the business is a separate legal entity like an LLC or corporation. The IRS uses this information to ensure accountability and proper tax administration.

Common Mistakes to Avoid

When applying for an EIN for your Connecticut business, avoiding common pitfalls can save time and prevent complications:

• Applying for an EIN when you already have one: An EIN is permanent. If you already have an EIN for your business, you generally do not need a new one unless there's a significant change in business structure (e.g., a sole proprietorship incorporates).
• Incorrectly identifying the responsible party: Ensure the responsible party's name and TIN are accurate and match IRS records. Discrepancies can delay processing.
• Choosing the wrong entity type: Carefully select the correct business entity type on Form SS-4. An incorrect selection may lead to tax filing errors later. For example, distinguish between a sole proprietorship, partnership, corporation, and LLC.
• Providing inaccurate business information: Double-check the business name, address, and other details for typos or errors.
• Applying multiple times: Only one EIN is issued per responsible party per day. Submitting multiple applications for the same entity will not expedite the process and can cause confusion.
• Using third-party services unnecessarily: While some services offer to obtain an EIN for a fee, the IRS application is free and straightforward. Be wary of services that charge for what you can do yourself for free.
• Not understanding when a new EIN is needed: Generally, a new EIN is needed if you change your business structure (e.g., from sole proprietorship to corporation), if you form a new partnership, or if you purchase an existing business and operate it as a different entity. A new EIN is typically not needed if you change your business name, location, or add new business locations.

By carefully reviewing the IRS instructions and your application details, you can ensure a smooth and efficient EIN acquisition process for your Connecticut business.

After Getting Your EIN in Connecticut

Once you have obtained your EIN for your Connecticut business, there are several important steps and considerations:

• Open a Business Bank Account: Most banks require an EIN to open a dedicated business checking or savings account. This is a crucial step for separating business finances from personal finances, which is especially important for LLCs and corporations to maintain liability protection.
• Register with Connecticut State Agencies: While the EIN is a federal tax ID, you will likely need it for state-level registrations.
  • Connecticut Department of Revenue Services (DRS): You will need your EIN to register your business with the DRS for state tax purposes, such as sales and use tax, withholding tax, corporation business tax, or other specific business taxes. The DRS provides an online business registration system.
  • Connecticut Department of Labor: If you have employees, you will need your EIN to register with the Department of Labor for unemployment insurance and other employer obligations.
• File Federal Tax Returns: Your EIN will be used on all federal tax forms and returns for your business, including Form 1120 (U.S. Corporation Income Tax Return), Form 1065 (U.S. Return of Partnership Income), or Form 941 (Employer's Quarterly Federal Tax Return).
• Apply for Business Licenses and Permits: Depending on your industry and location within Connecticut, you may need various federal, state, or local licenses and permits. Your EIN may be required on these applications.
• Keep Records: Keep your EIN confirmation letter (CP 575 notice) in a safe place with other important business documents. You will need this number for various official communications and filings.
• Understand Your Tax Obligations: An EIN is just the first step. Understand your federal and state tax obligations based on your business structure and activities. Consider consulting with a tax professional to ensure compliance.

The EIN is a foundational element for formal business operations in Connecticut, enabling compliance with federal and state regulations and facilitating financial management.

Frequently Asked Questions

How do I get an EIN for my Connecticut business?

The fastest way to get an EIN for your Connecticut business is to apply online directly through the IRS website. The application is free, and the EIN is typically issued immediately upon completion.

Is there a fee to get an EIN in Connecticut?

No, the IRS does not charge any fee to apply for or obtain an Employer Identification Number (EIN). The application is free regardless of whether you apply online, by mail, or by fax.

How long does it take to get an EIN for a Connecticut business?

If you apply online through the IRS website, you will typically receive your EIN immediately after completing the application. Mail applications can take several weeks, and fax applications take about four business days.

Does a single-member LLC in Connecticut need an EIN?

A single-member LLC in Connecticut that is treated as a disregarded entity by the IRS generally does not need an EIN unless it has employees or elects to be taxed as a corporation. Otherwise, it can use the owner's Social Security Number (SSN).

What information do I need to apply for an EIN?

You will need the name and taxpayer identification number (SSN, ITIN, or existing EIN) of the responsible party, the business name and address, the type of entity, and the reason for applying for the EIN.

Do I need an EIN to register my business with the Connecticut Secretary of State?

No, you typically do not need an EIN to register your business entity (like an LLC or corporation) with the Connecticut Secretary of State. The EIN is a federal tax ID, usually obtained after state registration.

Related Resources

• How to Get an EIN (main hub)
• How to Form an LLC in Connecticut
• Connecticut Business Tax Overview
• What is an ITIN?
• Business Legal Glossary
• How to Get an EIN in New York (sibling state)
• How to Get an EIN in Massachusetts (sibling state)

Sources

1. IRS - Employer ID Numbers (EINs).
2. IRS - How to Apply for an EIN.
3. IRS - Apply for an Employer Identification Number (EIN) Online.
4. IRS - About Form SS-4, Application for Employer Identification Number.
5. IRS - Taxpayer Identification Numbers (TIN).
6. Connecticut Department of Revenue Services - Business Taxes Overview.
7. Connecticut Department of Revenue Services - Business Registration Overview.
8. Connecticut Secretary of the State - Business Registration.
9. Connecticut Secretary of the State - Business Registration FAQs.
10. Cornell Law School Legal Information Institute - Employer Identification Number (EIN).
11. Cornell Law School Legal Information Institute - 26 U.S. Code § 6109 - Identifying numbers.
12. IRS - Limited Liability Company (LLC).
13. IRS - Do You Need a New EIN?.
14. Connecticut Department of Labor - Employer Information.
15. IRS - What is a Responsible Party?.

LegalGlass provides general information for educational purposes and is not a law firm or a substitute for advice from a licensed attorney or tax professional. Laws, fees, and thresholds change; verify current requirements with the IRS and relevant Connecticut state agencies before acting.