EIN Guide for an Arizona Limited Partnership

An Employer Identification Number is the nine-digit federal tax ID that the IRS hands out to businesses. It functions as the business equivalent of a Social Security number, identifying your partnership on tax filings, bank accounts, and other official paperwork.

For a limited partnership, the EIN is genuinely mandatory in a way it is not for every entity. A single-member LLC can sometimes get by using the owner's Social Security number, but a partnership cannot. A limited partnership files its own federal return — Form 1065 — and issues a Schedule K-1 to each partner. That means the partnership is a distinct tax filer with its own identity in the eyes of the IRS, and it needs its own EIN to file at all.

What you use the EIN for

• Filing the partnership's Form 1065 and issuing Schedule K-1s to the partners
• Opening the partnership's bank account — banks require it for a partnership
• Handling any employment taxes if the partnership hires employees
• Registering for Arizona transaction privilege tax if the business makes taxable sales

Because the partnership is its own filer, using an individual partner's Social Security number in place of an EIN is not an option. The EIN is the partnership's identity.

Timing matters. Apply for the EIN after the Arizona Secretary of State has recorded your Certificate of Limited Partnership, not before.

Why order matters

The EIN ties to a legally existing entity. If you apply before the partnership formally exists, you can create a mismatch between the IRS record and the state record — the partnership's legal name, formation, and existence should be settled first so the EIN attaches to a real entity with the correct name. Once the Secretary of State has recorded the certificate, the partnership exists, its exact legal name is fixed, and you can apply cleanly.

Where the EIN sits in the full sequence

1. Confirm the partnership name is available and file the Certificate of Limited Partnership
2. Have the Secretary of State record it, making the partnership legally exist
3. Apply for the EIN using the partnership's exact recorded name
4. Open the partnership's bank account, which requires both the recorded certificate and the EIN

Getting the EIN right after formation but before banking keeps the sequence clean and avoids having to correct a mismatched record later.

The IRS issues EINs at no cost, and the fastest route is the online EIN Assistant at IRS.gov. Any service that charges you specifically for the EIN is charging for convenience, not for the number, which is always free from the IRS directly.

The online application

The online EIN Assistant takes about ten minutes and issues the number immediately, so you can print the confirmation and use it the same day. You will select "partnership" as the entity type and provide the partnership's legal name exactly as it appears on the recorded certificate, its address, and information about the responsible party.

The responsible party

The IRS requires a "responsible party" on the application — the person who controls or manages the partnership, which for a limited partnership is typically a general partner. The responsible party completing the online application needs a valid U.S. Social Security number or ITIN.

If you have no SSN or ITIN

Applicants without a Social Security number or ITIN cannot use the online tool. Instead, they complete Form SS-4 and submit it to the IRS by fax or mail. This takes longer than the instant online issuance, so if a general partner lacks an SSN or ITIN, start the SS-4 process early so the EIN does not hold up banking.

A few recurring errors cause delays or cleanup work. Knowing them ahead of time keeps the process smooth.

Applying before the entity exists

As covered above, applying before the Secretary of State records the certificate can create a name or existence mismatch. Wait until the partnership legally exists.

Paying for a free number

The EIN is free from the IRS. If a third party bundles it into a fee, understand you are paying for someone to fill in a form you can complete yourself in about ten minutes.

Getting the legal name wrong

The name on the EIN application should match the recorded Certificate of Limited Partnership exactly. A mismatch between the IRS record and the state record can cause friction when opening bank accounts or filing returns.

Losing the confirmation

The EIN confirmation letter (the CP 575 for online applications) is the document banks and others may ask to see. Save a copy immediately. Getting a replacement from the IRS later is possible but slower than simply keeping the original.

Assuming one EIN covers multiple entities

If your structure uses a separate LLC as the general partner, that LLC is its own entity with its own EIN. Do not try to use one EIN for both the LLC and the limited partnership — each legal entity needs its own.

It helps to be clear about the EIN's limits, because people sometimes expect it to do more than it does.

The EIN is federal, not a state registration

Getting an EIN does not register your partnership with Arizona, and it does not replace filing the Certificate of Limited Partnership. It is purely a federal tax identifier. Your partnership's legal existence comes from the Secretary of State recording the certificate; the EIN just gives the federal government a way to identify the entity for tax purposes. The two are separate steps, and having one does not satisfy the other.

The EIN does not choose your tax treatment

Obtaining an EIN does not, by itself, elect any particular tax treatment. A limited partnership is taxed as a partnership by default — filing Form 1065 and issuing K-1s — regardless of the EIN. If a partnership ever wanted different federal tax treatment, that would be a separate election filed with the IRS, not something the EIN application decides. For the vast majority of limited partnerships, the default partnership treatment is exactly what you want, and the EIN simply supports it.

The EIN does not expire

Once issued, an EIN stays with the partnership for its life. You do not renew it and it does not lapse. If the partnership dissolves, the EIN is not reassigned to anyone else — the IRS retires it with the entity. You only need a new EIN if the fundamental structure changes in a way the IRS treats as a new entity, which is uncommon for a stable partnership.