Printable Form 2026

IRS Publication 1635 – Understanding Your EIN

IRS Publication 1635 – Understanding Your EIN – In the world of business taxation, navigating IRS requirements can feel overwhelming, but resources like IRS Publication 1635 make it easier. Titled “Understanding Your EIN,” this essential document from the Internal Revenue Service (IRS) breaks down everything you need to know about Employer Identification Numbers (EINs). Whether you’re a sole proprietor starting a new venture, a corporation expanding operations, or managing a trust or estate, this guide explains the purpose, application process, and maintenance of an EIN. As of 2026, the principles outlined in the latest revision (February 2014) remain relevant, though always check the IRS website for any updates.

This SEO-optimized article draws from trusted IRS sources to provide clear, actionable insights. We’ll cover what an EIN is, who needs one, how to apply, and specific considerations for different business entities. By the end, you’ll have a solid understanding to ensure compliance and avoid common pitfalls.

What Is an Employer Identification Number (EIN)?

An EIN is a unique nine-digit number (formatted as XX-XXXXXXX) issued by the IRS to identify business entities for tax purposes. It’s essentially the business equivalent of a Social Security Number (SSN) but is used exclusively for business activities. The IRS assigns EINs to employers, sole proprietors, corporations, partnerships, non-profit organizations, trusts, estates, government agencies, and certain individuals who file business-related tax returns.

Key points about EINs include:

  • They’re required for filing business tax returns, making tax payments, and submitting documents to the IRS and Social Security Administration (SSA).
  • EINs are not interchangeable with SSNs; you can’t use one in place of the other.
  • For employee benefit plans, an EIN might include an alpha character (like “P”) or a plan number (e.g., 003).
  • Since May 21, 2012, the IRS limits EIN issuance to one per responsible party per day, regardless of the application method.
  • Businesses should only have one EIN; if you have multiple, contact the IRS Business and Specialty Tax Line at 1-800-829-4933 to determine the correct one.

If you haven’t received your EIN by the time a tax return is due, simply write “Applied For” along with the application date on the form.

Who Needs an EIN and When to Get a New One?

Not every business or entity requires an EIN, but it’s mandatory if you:

  • Have employees.
  • Operate as a corporation or partnership.
  • File employment, excise, or alcohol/tobacco/firearms tax returns.
  • Withhold taxes on income paid to non-resident aliens.
  • Manage trusts, estates, or certain retirement plans.
  • Run a non-profit or exempt organization.

Even sole proprietors without employees might need an EIN for opening a business bank account, applying for business licenses, or establishing a Keogh or solo 401(k) plan.

The need for a new EIN depends on your business structure and changes. Here’s a breakdown by entity type:

Sole Proprietorships

A sole proprietorship is an unincorporated business owned by one individual, with no legal separation from the owner. You file taxes via Schedule C, C-EZ, or F on Form 1040.

  • When a New EIN Is Needed: If you file for bankruptcy (Chapter 7 or 11), incorporate, take on partners to form a partnership, or establish a pension, profit-sharing, or retirement plan.
  • When It’s Not Needed: For name or location changes, adding new locations, or operating multiple businesses under the same structure.
  • Special Note for Single-Member LLCs: Treated as disregarded entities unless filing employment or excise taxes; report on your personal Schedule C or F.

Corporations

Corporations are separate legal entities from their owners, liable for their own debts. They file Form 1120 series returns.

  • When a New EIN Is Needed: Becoming a subsidiary of another corporation, converting to a partnership or sole proprietorship, forming a new corporation after a merger, or receiving a new charter.
  • When It’s Not Needed: For divisions of an existing corporation, name or location changes, electing S corporation status (via Form 2553), or certain reorganizations that don’t change the entity’s identity.

Partnerships

Partnerships involve two or more people carrying on a trade or business, sharing profits. They file Form 1065.

  • When a New EIN Is Needed: Incorporating, one partner becoming the sole owner, or terminating the old partnership to start a new one.
  • When It’s Not Needed: For name or location changes, or terminations under IRC Section 708(b)(1)(B) (e.g., sale of 50% or more interest within 12 months).

For husband-and-wife businesses, you may qualify as a joint venture (taxed as sole proprietors) if filing jointly and both materially participate—no joint EIN needed.

Estates and Trusts

Estates handle a deceased person’s assets until distribution, while trusts hold property for beneficiaries.

  • Estates: New EIN needed if a trust is created from estate funds or if the estate operates a business after death. Not needed for changes in fiduciaries or beneficiaries.
  • Trusts: New EIN for changes from trust to estate, living to testamentary, or revocable to irrevocable. Not needed for name or address changes. Separate EINs for multiple trusts by the same grantor.

Employee Plans and Exempt Organizations

  • Employee Plans: Use the sponsor’s EIN if possible; file Form 5500 series.
  • Exempt Organizations: All need an EIN before applying for exemption (Form 1023 or 1024); file Form 990 series. Group exemptions allow central organizations to cover subordinates.

Limited Liability Companies (LLCs)

LLCs offer liability protection. Tax treatment defaults to partnership (multi-member) or disregarded entity (single-member). You can elect corporate taxation via Form 8832.

  • Single-member LLCs owned by individuals are disregarded for income tax but not for employment/excise taxes after 2009.

How to Apply for an EIN: Step-by-Step Process?

Applying for an EIN is free and straightforward through the IRS. Avoid third-party sites that charge fees.

  1. Online Application: The fastest method—visit IRS.gov and search for “EIN.” Complete the interview-style application Monday through Friday, 7 a.m. to 10 p.m. ET. You’ll receive your EIN immediately if eligible. Requires a valid Taxpayer Identification Number (TIN) for the responsible party.
  2. Fax: Submit Form SS-4 to the appropriate IRS fax number based on your state. Expect your EIN in about 4 business days.
  3. Mail: Send Form SS-4 to the IRS service center for your location. Processing takes around 4 weeks.

Before applying, form your legal entity (e.g., LLC) if applicable. International applicants without a U.S. TIN can apply by phone or mail.

Completing Form SS-4: Tips for Accuracy

Form SS-4 is the Application for Employer Identification Number. Download it from IRS.gov or call 1-800-TAX-FORM. Key lines vary by entity, but general tips include:

  • Use only A-Z, 0-9, hyphens, and ampersands in names; spell out symbols.
  • Identify the “responsible party”—the person or entity controlling funds (not a nominee).
  • Optionally authorize a Third Party Designee (TPD) to receive your EIN.
  • Specify reasons like starting a new business, hiring employees, or banking purposes.

For specific entities:

  • Sole Proprietors: Enter your full name on Line 1, SSN/ITIN on Line 9a.
  • Corporations: Use the charter name on Line 1; check “Corporation” on Line 9a.
  • Trusts: List the trust name on Line 1; grantor’s TIN on Line 9a.
  • Include start dates, employee counts, and business descriptions where applicable.

EIN Responsibilities: Employment and Excise Taxes

Once you have an EIN, use it for:

  • Employment Taxes: Withholding income tax, FICA (Social Security/Medicare), and FUTA. File Forms 941, 940, or 944.
  • Excise Taxes: For activities like fuel sales or wagering; file Form 720.

Maintain accurate records and update the IRS for changes in address or responsible party via Form 8822-B.

Canceling or Changing an EIN

EINs are permanent and can’t be canceled, but you can close your account by writing to the IRS with details. If your business changes structure (e.g., sole prop to corporation), apply for a new EIN.

Final Thoughts on IRS Publication 1635

IRS Publication 1635 is an invaluable resource for demystifying EINs, ensuring businesses stay compliant with tax laws. By understanding when and how to obtain an EIN, you can avoid delays in filings and penalties. For the most current information, always refer directly to IRS.gov, as tax rules can evolve. If you have specific questions, consult a tax professional or contact the IRS.