EIN Guide for a Connecticut Corporation

An Employer Identification Number is a nine-digit number the IRS assigns to identify a business for federal tax purposes. It's often called a federal tax ID or FEIN, and it functions as the business equivalent of a Social Security number. Where an SSN identifies you as an individual, the EIN identifies your corporation as a separate taxpayer.

Why a corporation always needs one

Unlike a single-member LLC, a corporation is never a "disregarded entity" — it's always a separate taxpayer in the eyes of the IRS. That means a corporation cannot use an owner's Social Security number for its tax and banking life. It needs its own EIN from the day it starts operating. You'll use the EIN to:

• File the corporation's federal tax return.
• Open a corporate bank account — banks require it.
• Hire employees and run payroll.
• Make an S corporation election, which is filed under the corporation's EIN.
• Apply for business licenses and set up vendor and merchant accounts.

There's no scenario where a Connecticut corporation operates without an EIN, so getting one is a standard early step right after formation.

The right sequence is to form the corporation first, then get the EIN. The IRS asks for the corporation's legal name and formation details on the application, so you want the Certificate of Incorporation processed before you apply. Applying before the entity exists can produce a mismatch between the EIN and the corporate record.

The natural order

1. File the Certificate of Incorporation and get it processed by the Connecticut Secretary of the State.
2. Apply for the EIN once the corporation legally exists.
3. Use the EIN to open the corporate bank account, set up payroll, and make any tax elections.

Getting the EIN promptly after formation clears the way for everything downstream — you can't open the bank account or run payroll without it, and both tend to be on the early to-do list.

The IRS issues EINs directly and at no cost. The fastest route is the online application, which gives you the number immediately.

Applying online

Use the IRS EIN Assistant. The application is free, takes about ten minutes, and issues the EIN on the spot so you can download the confirmation and use the number the same day. The online tool is available during posted IRS hours and must be completed in one session — it times out if you leave it idle.

What you'll need

• The corporation's exact legal name and Connecticut formation details.
• The business mailing address.
• The responsible party — an individual who controls the corporation, along with their Social Security number or ITIN.
• The reason you're applying (starting a new business) and the expected number of employees.

If you don't have an SSN or ITIN

The online tool requires the responsible party to have a US Social Security number or ITIN. If yours doesn't, you can still get an EIN by submitting Form SS-4 to the IRS by fax or mail. It takes longer than the instant online issuance, but the EIN itself is still free.

The IRS requires every EIN application to name a "responsible party" — the person who ultimately owns or controls the corporation, or who exercises effective control over it. For a corporation, this is typically a principal officer, a controlling shareholder, or another individual with genuine authority over the company.

What the responsible party is for

The responsible party is the natural person the IRS holds accountable for the entity behind the EIN. It has to be an individual with a valid taxpayer ID, not another business entity (with narrow exceptions), and the IRS expects the information to stay current.

Keeping it current

If the responsible party changes — say control of the corporation shifts — the IRS expects you to update the record using Form 8822-B. Keeping the responsible party accurate matters because that's who the IRS contacts about the corporation's federal tax matters.

Getting the EIN is simple, but a few avoidable errors cause real headaches later.

What to watch for

• Paying for an EIN. The IRS never charges for an EIN. Third-party sites that charge for "EIN filing" are charging for convenience, not for the number — you can always get it free directly from the IRS.
• Applying before the corporation exists. Get the Certificate of Incorporation processed first so the EIN matches your legal entity. An EIN tied to a name that doesn't match your corporate record causes friction at the bank.
• Name mismatches. Enter the corporation's exact legal name as it appears on the Certificate of Incorporation. Small discrepancies between the EIN record and the state record can hold up bank accounts.
• Losing the confirmation. Save the EIN confirmation letter (the CP 575 the IRS issues online). Banks and lenders ask for it, and it's the cleanest proof of your EIN.
• Using your SSN instead. A corporation is a separate taxpayer — don't run its taxes or accounts under a personal SSN. Get the EIN and use it consistently.

How Mainstay Filing helps

If you'd rather not deal with the IRS application yourself, we can obtain the EIN for your Connecticut corporation as part of formation, so your entity comes with its federal tax ID ready to go. You still pay nothing extra to the IRS for the number itself — a filing service simply handles the application on your behalf so you have the EIN in hand alongside your stamped Certificate of Incorporation.