EIN Guide for a South Dakota Corporation

An Employer Identification Number (EIN), also called a Federal Tax Identification Number, is a nine-digit number the IRS assigns to identify a business entity for federal tax purposes. Think of it as a Social Security number for your corporation.

Why a corporation always needs one

Unlike a single-member LLC — which can sometimes get by using the owner's Social Security number — a corporation always needs its own EIN. A corporation is a separate taxpayer that files its own federal return (Form 1120 for a C corporation, Form 1120-S for an S corporation), so there's no scenario in which it uses an individual's SSN. The moment you incorporate, an EIN is on your to-do list.

What you'll use the EIN for

• Filing the corporation's federal income tax return
• Opening a corporate bank account (banks require it)
• Running payroll and filing employment tax returns
• Establishing the corporation's identity with vendors, lenders, and payment processors
• Applying for business licenses and permits that ask for a federal tax ID

Timing matters. There's a right point in the formation sequence to get your EIN.

Incorporate first

Apply for the EIN after your Articles of Incorporation are filed and your corporation legally exists. The EIN application asks for the corporation's legal name and formation details, so the corporation needs to be on the state's records first. Applying before the corporation exists can create a mismatch you'll have to untangle later.

Then apply promptly

Once the corporation is formed, get the EIN right away. It's the gate to nearly everything else — you can't open the bank account, issue stock cleanly, or set up payroll without it. Since the online application issues the number immediately, there's no reason to delay.

Before the bank

Make sure you have the EIN in hand before your bank appointment. Banks require the EIN confirmation to open a corporate account, alongside your filed Articles of Incorporation and your bylaws or organizational minutes. Showing up without the EIN means a wasted trip.

The IRS issues EINs directly, at no cost. Be skeptical of any service that charges a standalone fee just to obtain one — the application is quick and free if you do it yourself.

The online application

The fastest method is the IRS online EIN Assistant at IRS.gov. The application takes about ten minutes, and the EIN is issued immediately at the end — you can download the confirmation letter and start using 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 to complete it

• The corporation's legal name and South Dakota address, exactly as filed
• The type of entity (corporation) and the reason for applying (started a new business)
• The name and taxpayer ID of the responsible party — the individual who controls or directs the corporation
• Information about expected employees and business activity

The responsible party

The IRS requires a responsible party with a U.S. Social Security number or ITIN to complete the online application. This is typically a principal officer or controlling shareholder. If the responsible party doesn't have an SSN or ITIN, you can't use the online tool — you'll apply by fax or mail instead.

Non-U.S. founders can still get an EIN for a South Dakota corporation; the process is just slower.

Fax or mail Form SS-4

If the responsible party has no SSN or ITIN, complete IRS Form SS-4 and submit it by fax or mail. On the responsible party's tax ID line, you write "Foreign" if they have no U.S. tax ID. Fax is faster than mail — the IRS typically returns an EIN by fax within a few business days, versus several weeks for mailed applications.

Plan for the lead time

Because the non-SSN route can't be done online instantly, build the extra time into your schedule. If you're a foreign founder who needs the EIN to open a bank account or start operating, apply as soon as the corporation is formed so the wait doesn't hold up everything else.

Keep it accurate

Whatever route you use, make sure the corporation's name and details on the application exactly match what's on your Articles of Incorporation. Mismatches between your EIN records and your state formation records cause problems with banks and the IRS down the line.

Getting the number is the milestone, but a few follow-ups keep it useful and safe.

Store the confirmation letter

The IRS issues an EIN confirmation (the CP 575 letter for mailed/faxed issuance, or an immediate PDF online). Save it somewhere permanent. Banks and agencies sometimes ask for it, and getting a replacement (a 147C letter) from the IRS takes time and a phone call.

One EIN per corporation

Your corporation needs exactly one EIN, and it stays with the corporation for life. You don't get a new one when you change your address, add shareholders, or change officers. A new EIN is generally only needed if the entity's fundamental structure changes — for example, converting to a different entity type. Don't apply twice.

Guard it, but know it's semi-public

Treat the EIN with reasonable care, but understand it's not a secret the way an SSN is — it appears on many business documents. Use it confidently on tax filings, bank paperwork, and vendor forms, while still avoiding posting it carelessly.

S-corp election is separate

Getting an EIN does not make your corporation an S corporation. If you want S-corp tax treatment, that's a separate election — filing Form 2553 with the IRS within the applicable window. The EIN is just the tax ID; the S election is a distinct decision to discuss with your CPA.