Getting an EIN for Your Wisconsin Corporation — A Complete Guide

An Employer Identification Number (EIN) is a nine-digit number the IRS assigns to identify a business for federal tax purposes. Think of it as a Social Security number for your corporation — the unique identifier the federal government uses to track the entity.

Every corporation needs one

Unlike a single-member LLC, which can sometimes operate on the owner's Social Security number, a corporation always needs its own EIN. A corporation is a separate taxpayer that files its own returns (Form 1120 for a C corporation, Form 1120-S for an S corporation), so it must have its own federal ID. There's no version of running a corporation without an EIN.

What you'll use it for

• Filing corporate tax returns with the IRS
• Opening a business bank account — banks require the EIN for a corporation
• Hiring employees and handling payroll tax
• Registering for Wisconsin state taxes with the Department of Revenue
• Applying for business licenses and permits that ask for a federal tax ID
• Establishing business credit in the corporation's name

The EIN is one of the first things you'll be asked for repeatedly, so getting it early removes a bottleneck from everything that follows formation.

Timing matters. Apply at the right point and everything downstream goes smoothly.

Form the corporation first

Apply for the EIN after your Articles of Incorporation are filed and the corporation legally exists. The EIN application asks for the corporation's legal name and formation details, so the entity should be on file with DFI first. Applying before the corporation exists can create a mismatch between the IRS record and your actual entity name.

Apply before you need to act

Once the corporation is formed, get the EIN promptly. You'll need it to open the corporate bank account, and you can't really operate — take in money, pay expenses, run payroll — until that account exists. Founders who wait on the EIN often find themselves stalled at the bank. Getting it right after formation keeps momentum.

The IRS issues EINs directly, and it's free. Be careful of third-party sites that charge a fee to "get" an EIN — the IRS never charges for it.

Option 1: Apply online (fastest)

The IRS online EIN application is the quickest route. If the responsible party has a Social Security number or ITIN, you complete the application in one session and the EIN is issued immediately at the end. A few things to know:

• The application is available during posted IRS hours, not around the clock
• You must finish in one sitting — it times out after a period of inactivity
• The responsible party is the individual who controls the corporation (an owner or principal officer). The IRS wants a real person here, not the entity itself

Option 2: Apply by fax or mail

If you can't use the online tool — for example, if the responsible party doesn't have an SSN or ITIN — you file IRS Form SS-4 by fax or mail. Fax takes several business days; mail takes several weeks. International applicants without an SSN can also apply by phone through the IRS.

What you'll need

• The corporation's exact legal name as filed with DFI
• The corporation's Wisconsin address
• The responsible party's name and SSN or ITIN
• The date the corporation was formed and the reason for applying (started a new business)
• The number of employees you expect and your principal business activity

A few predictable errors cause most EIN headaches. They're all easy to sidestep.

Paying for an EIN

The EIN is free from the IRS. If a website is charging you a fee just to obtain the number, you're paying for something the government gives away. Some formation services bundle EIN handling into a paid package, which is a convenience, but the number itself has no government cost.

Name mismatch

The name on the EIN application must match your filed corporate name exactly. A mismatch between your IRS record and your DFI record can cause problems with banks and future filings. Apply after formation and copy the name precisely.

Wrong responsible party

The responsible party must be an individual with real control over the corporation and a valid taxpayer ID — not the corporation itself and not a nominee. Naming the wrong person, or trying to list the entity, causes rejections.

Applying too early or twice

Don't apply before the corporation is formed, and don't apply twice thinking the first one didn't go through. If you're unsure whether you already have an EIN, contact the IRS rather than filing a duplicate — a corporation should have exactly one.

The EIN is federal, but it's the key that unlocks your state-level tax registrations too.

Wisconsin Department of Revenue

Once you have the EIN, you'll use it to register with the Wisconsin Department of Revenue for the state taxes that apply to your corporation — which can include corporate income and franchise tax, and, if you sell taxable goods or services, sales and use tax. The Department of Revenue is separate from DFI, where you formed the corporation, so this is a distinct step.

Employer registrations

If your corporation has employees — including owner-employees who take a salary, common with an S election — you'll use the EIN to set up federal payroll tax deposits and Wisconsin withholding and unemployment insurance accounts.

Keep the EIN somewhere safe

Once issued, the EIN confirmation notice (the IRS calls it the CP 575) is an important document. Store it with your corporate records. You'll be asked for the EIN constantly, and having the official confirmation on hand smooths bank and vendor onboarding.

How we fit in

When you form your corporation with Mainstay Filing, we can point you to the EIN step as part of getting set up, and our focus stays on the DFI formation and registered agent side. The EIN application itself is quick and free directly from the IRS, and we'd rather you not pay anyone unnecessarily for a number the government issues at no cost.