EIN Guide for a South Dakota LLP

An Employer Identification Number 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 partnership — the identifier that ties together your tax filings, your business bank account, and your payroll.

An LLP always needs one

Unlike a single-member LLC, which can sometimes get by on the owner's Social Security number, a limited liability partnership always needs its own EIN. The reason is structural: an LLP has two or more partners and is taxed as a partnership by default, which means it files a federal partnership return. That return is filed under the EIN, so there is no version of running an LLP where you can skip getting one.

What you use it for

• Filing the partnership's federal return (Form 1065) and issuing Schedule K-1s to the partners
• Opening a business bank account — banks require the EIN for a partnership
• Hiring and paying employees, including payroll tax deposits and returns
• Registering for state accounts, such as a South Dakota sales tax license, which reference the EIN

The IRS issues EINs at no charge. This is worth stating plainly because plenty of services advertise "EIN filing" for a fee — what they are charging for is filling out a free federal form on your behalf, not the number itself. You can get one directly in a few minutes.

The online application

Your quickest option is the IRS EIN Assistant, available at IRS.gov. The online application:

• Is free
• Takes roughly ten minutes to complete
• Issues the EIN immediately at the end, so you can download the confirmation and use the number the same day
• Is available during the IRS's posted hours for the tool

What you need before you start

• The partnership's legal name exactly as registered with the South Dakota Secretary of State
• The type of entity (a partnership) and the number of partners
• The name and taxpayer identification number of the responsible party — a partner who controls or manages the LLP
• The partnership's principal business address and a brief description of its activity

If you can't apply online

The online application requires the responsible party to have a US Social Security number or ITIN. If the responsible party does not have one, you apply using Form SS-4 by fax or mail. This is slower — fax takes several business days and mail takes weeks — so plan ahead if this applies to your partnership.

The EIN fits into a natural order alongside your other setup steps, and getting the sequence right saves you from redoing work.

Register the LLP first, then get the EIN

It is generally cleanest to register your LLP with the South Dakota Secretary of State first, then apply for the EIN. That way the partnership's legal name is settled, and the name on your EIN matches the name on your state registration. Applying for an EIN before your partnership name is finalized risks a mismatch you would have to correct later.

Then open the bank account

With the accepted state registration and the EIN in hand, you can open the partnership's bank account. Most banks want both documents, plus the partnership agreement and ID for the authorized signers. Keeping partnership money in its own account is essential to preserving the LLP's liability shield and to clean bookkeeping among partners, so opening the account promptly after you have the EIN is the right move.

An EIN is durable, but a few situations around it trip people up.

One EIN for the life of the partnership

In most cases your LLP keeps the same EIN for as long as it exists. You do not get a new one each year or each time you file. Certain structural changes — such as reorganizing the entity — can require a new EIN, but ordinary events like adding a partner or changing your address generally do not.

Changing information tied to the EIN

If the partnership's address, responsible party, or name changes, you update that information with the IRS rather than applying for a new number. Keeping the IRS record accurate matters, because that is where tax correspondence and notices are directed.

Guard the confirmation

Keep your EIN confirmation letter (the IRS calls it the CP 575) somewhere safe and accessible. Banks and agencies sometimes ask for it, and while the number itself is easy to remember, the official confirmation is the document that proves it. Store it with your state registration and partnership agreement so your core formation records are all in one place.

Mainstay Filing focuses on the state-facing work — registering your LLP with the South Dakota Secretary of State and, if you choose, serving as your registered agent. The EIN itself comes from the IRS, and because it is free and quick, we point you to the right place to get it rather than charging you for a form you can complete yourself in minutes.

What we make sure of is that your state registration is done correctly first, so that when you apply for the EIN, the partnership name and details line up cleanly with your official record. Getting that order right avoids the small mismatches that turn into annoying corrections later.

A note on advice

We handle filings, not tax strategy. Questions about how your LLP should be taxed, whether any election makes sense for your situation, or how to structure partner compensation are conversations for a CPA. The EIN is simply the identifier that makes all of that possible, and getting it is one of the easier steps in standing up your partnership.