The IRS EIN Assistant: How the Online EIN Application Works

What the EIN Assistant is

EIN Assistant is the IRS’s own name for the tool, and the name on the button at irs.gov. People also call it the online SS-4, the EIN online application, or the IRS EIN website; they are all the same page. It asks the questions on Form SS-4 one screen at a time, checks the answers against IRS records as you go, and prints the EIN with the CP 575 confirmation letter when the application passes. There is no account, no login and nothing to download.

The IRS rebuilt the tool in 2026. The address changed, the pages were reordered, a postal address check was added, and four excise tax questions that used to be buried in a sub screen are now asked of everyone. The rules did not change: same hours, same one sitting, same one EIN per day, same SSN or ITIN requirement. The walkthrough below follows the rebuilt tool.

Before you start: what ends a session

• Hours. The tool is open Monday to Friday 6 a.m. to 1 a.m. (into the next day), Saturday 6 a.m. to 9 p.m., and Sunday 6 p.m. to midnight, Eastern time, and offline the rest of the time and for maintenance. Starting a few minutes before it closes is a common way to lose the session. The live IRS EIN hours tool shows whether it is open right now, in your time zone.
• 15 minutes idle. Any pause longer than that, such as going to find the formation certificate, ends the session with nothing saved.
• One sitting. There is no save, no resume, and the browser back button often resets the form.
• One per day. A responsible party can be issued one EIN per day through the tool. A second application the same day returns reference number 114.
• SSN or ITIN required. The responsible party must enter their own SSN or ITIN. Since 2019 the tool does not accept an EIN in that field, so an entity cannot be the responsible party.
• U.S. address required. A business with no address in the United States or its territories applies by fax or by the international phone line instead.

Have these ready

• The legal name exactly as the state approved it, including the LLC or Inc suffix as the state wrote it. The tool rejects most punctuation, so a name with an apostrophe or a comma is entered without it.
• The formation or incorporation date from the state certificate, or the date a sole proprietorship started.
• The responsible party’s full legal name and SSN or ITIN, matching Social Security records.
• The physical business address, not a PO box, and the county.
• Number of members for an LLC, and whether it will elect corporate taxation.
• What the business does, in a sentence, and whether it expects employees in the next year.
• Whether the business will owe any excise tax: heavy highway vehicles, wagering, alcohol, tobacco or firearms, or anything filed on Form 720. For most new businesses every answer is no.
• A fax number is not needed online, but a printer or a place to save a PDF is.

The pages, in order

1. Legal structure

Sole proprietor, partnership, corporation, LLC, estate, trust, or one of the less common types. An LLC then answers how many members it has, which state it was organized in and, for a single member, whether it will be taxed as a corporation. This page sets the tax classification the IRS records, and it is the one to read twice: an LLC that picks “corporation” here without filing Form 8832 or 2553 gets an IRS letter months later.

2. Reason for applying

Started a new business, hired employees, banking purposes, changed type of organization, or purchased a going business. For a new entity the first option is correct even if the bank is the immediate reason. The answer sets which returns the IRS expects.

3. Responsible party

The person’s name and SSN or ITIN, and whether they are an owner, officer, partner, trustee or executor, or a third party applying on the entity’s behalf. The tool checks the name against Social Security records; a nickname, a maiden name or a missing hyphen produces reference number 102 or 103.

4. Third party designee

Shown only when the previous page said a third party is applying. The designee’s name, address and phone, which must differ from the applicant’s own; identical details are the cause of reference number 104.

5. Addresses

The physical location, a phone number and, if different, a mailing address. A registered agent’s office entered as the physical address is a common mistake; the IRS wants where the business actually is.

6. Address verification

The rebuilt tool checks the address against the postal database and offers the standardized version. Accept it unless it has changed the suite or unit number; the choice affects where the CP 575 goes if it is mailed.

7. Business details and the excise questions

Legal name, trade name if any, the start date, the closing month of the accounting year, whether the business expects employees and how many, and four yes or no questions about excise taxes. The name check happens here: a name that conflicts with an existing record returns reference number 101 at the end.

8. Activity

The principal activity chosen from a short list (retail, construction, real estate, health care and so on) with a follow up question and a one line description. Pick “other” and describe the business when nothing on the list fits; the choice is statistical and does not affect the EIN.

9. Review, confirmation choice and submit

Every answer on one page, with the choice of receiving the CP 575 online as a PDF or by mail. Choose online: the PDF is offered once, and the IRS does not mail a copy to online applicants who took it. Check the legal name character by character against the state certificate, then submit. The EIN appears immediately when the application passes, with the legal name, the name control and the organization type the IRS recorded, and the CP 575 link beside it.

When you get a reference number instead of an EIN

The tool does not explain its reference numbers. In short: 101 is a name conflict, 102 and 103 are a responsible party name or SSN mismatch, 104 is a third party designee conflict, 105 is a lockout from too many attempts, 109 through 113 are IRS side errors worth one retry, 114 is the one per day limit, and 115 is a Social Security record problem. The reference number guide has each one with its fix. Do not resubmit blindly: 101 will return every time, and repeated attempts earn a 105. If the tool itself will not load or the session keeps dying, the not working guide goes through the causes in order.

After the number is issued

• Save the CP 575 PDF in two places. Banks ask for it and the IRS does not reissue it.
• The EIN is usable immediately for a bank account and most purposes. Some IRS systems, including electronic filing and payments, take up to two weeks to recognize a new number.
• If you elected corporate taxation on page 1, file Form 2553 or 8832 within the deadline; the EIN application does not make the election for you.
• There is no status page afterwards and nothing to check. The application status guide covers the one ambiguous case, a session that closed after submit.

Quick answers

What is the IRS EIN Assistant?

The IRS’s name for its online EIN application, the page on irs.gov where a business applies for an employer identification number and receives it in the same session. It is the same thing people call the online SS-4 or the EIN online application. There is no account to create and nothing to download.

Can a third party apply online for me?

Yes. A third party designee can complete the online application on behalf of the business with the responsible party’s authorization, which is how filing services, accountants and attorneys do it. The responsible party’s own SSN or ITIN is still what goes on the form.

How long does the online application take?

About ten minutes when everything is ready, and the EIN appears on the final page the moment the application passes. The time is spent before you start, gathering the exact legal name, dates and the responsible party’s details; the pages themselves are quick.

What if I do not have an SSN or ITIN?

The EIN Assistant will not accept the application. Fax or the international phone line are the routes; the no SSN guide covers both.

I closed the window before saving the CP 575. Now what?

The EIN was still issued and is valid. The notice is gone, and the replacement is a 147C verification letter requested by phone. Do not apply again. The confirmation letter guide has the call.