How to Get an EIN in Colorado (2026)

Fact-checked by the LegalGlass editorial team against primary sources · Published Aug 6, 2026 · Last updated Aug 6, 2026

To get an Employer Identification Number (EIN) for a business in Colorado, you apply directly with the Internal Revenue Service (IRS). The EIN is a federal tax identification number, not a Colorado-specific ID, and it is issued free of charge ($0). The fastest method is the IRS EIN Assistant, which delivers the number immediately once the online application is complete.

What Is an EIN and Why Do You Need One in Colorado?

An Employer Identification Number (EIN), also called a Federal Tax Identification Number, is a unique nine-digit number the IRS assigns to identify a business for federal tax purposes. It functions for a business the way a Social Security Number (SSN) does for an individual. Although the EIN is a federal identifier issued by the IRS - not by the Colorado Secretary of State or the Colorado Department of Revenue - nearly every business operating in Colorado needs one to meet federal and state tax obligations, hire workers, and open bank accounts. For background on the number itself, see what is an EIN and the broader how to get an EIN guide.

Reasons a Colorado Business Needs an EIN

• Hiring employees: Any Colorado business that pays wages must have an EIN to report federal payroll taxes to the IRS and to register for Colorado wage withholding with the Department of Revenue.
• Forming a corporation or partnership: All corporations (including S-corporations) and partnerships must have an EIN, whether or not they have employees.
• Forming a multi-member LLC: A Colorado LLC with more than one member is taxed as a partnership by default and must obtain an EIN. See how to get an EIN for an LLC.
• Electing corporate tax status: Even a single-member LLC that would otherwise use the owner's SSN must get an EIN if it elects to be taxed as a corporation or S-corporation.
• Opening a business bank account: Most banks require an EIN even for sole proprietors and single-member LLCs. See EIN and business bank accounts.
• Registering for Colorado taxes: A federal EIN is used when you apply for a Colorado sales tax license or wage withholding account with the Department of Revenue.

The IRS explains the full list of triggers on its Do You Need an EIN? page. If you are unsure whether your structure requires one, review how to start a business in Colorado and sole proprietorship rules first.

How to Apply for an EIN in Colorado (Step by Step)

Because the EIN application is federal, the process is identical in Colorado to every other state. There are four methods, differing mainly in speed. The online tool is by far the most common.

Method 1: Apply Online (Recommended, Instant EIN)

The IRS EIN Assistant is available Monday through Friday, 7 a.m. to 10 p.m. Eastern Time, and issues the number immediately upon completion.

1. Open the IRS EIN Assistant. Go to the official IRS EIN online application and click "Apply Online Now."
2. Provide business information. Enter the legal name and mailing address of the business, the entity type (sole proprietor, partnership, corporation, or LLC), and the reason for applying.
3. Enter responsible-party details. Give the name and Taxpayer Identification Number (SSN, ITIN, or existing EIN) of the responsible party who controls the entity.
4. Receive your EIN. If the application is valid, the IRS issues the EIN on the spot. Download and save the CP 575 confirmation letter, because you cannot retrieve it online later.

Important: the session cannot be saved and resumed, and the IRS grants only one EIN per responsible party per day.

Method 2: Apply by Fax

Faxing Form SS-4 is the next-fastest option and works when the online tool is unavailable.

1. Complete Form SS-4 in full, including the responsible party's SSN, ITIN, or existing EIN.
2. Fax it to the IRS. For a business located in Colorado, the fax number is 855-641-6935.
3. If you provide a return fax number, the IRS faxes the EIN back in about four business days.

Method 3: Apply by Mail

Mail is the slowest route and is best only when faxing and the online tool are not options.

1. Complete Form SS-4.
2. Mail it to the address for domestic applicants:
   Internal Revenue Service
   Attn: EIN Operation
   Cincinnati, OH 45999
3. The IRS mails the confirmation letter in roughly four to six weeks.

Method 4: Apply by Phone (International Applicants Only)

This method is reserved for applicants with no legal residence or principal place of business in the U.S. Call 267-941-1099 (not toll-free), answer the Form SS-4 questions, and the representative assigns the EIN by phone. For the full method comparison, see the IRS page on how to apply for an EIN.

EIN Cost and Processing Times in Colorado

The EIN itself is always free from the IRS - no Colorado agency charges for it, and no third-party service is required. The only difference between the methods is how quickly you receive the number. Third-party filing services may add a fee, but they are optional; you can always apply directly at no cost, and websites that charge for a "free EIN number" are simply reselling a federal service.

If you already obtained a number but misplaced it, you do not reapply - see how to find a lost EIN or use the EIN lookup guide. You cannot get a second EIN to replace one you already hold for the same entity.

The Responsible Party Requirement

Every EIN application must name a "responsible party" - the individual who ultimately owns or controls the entity or directs its finances. The IRS limits this to a natural person (except for government entities), not another company. For common Colorado structures:

• Sole proprietorship: the sole proprietor.
• Partnership: a general partner.
• Corporation: a principal officer, such as the president or CEO.
• LLC: the sole member for a single-member LLC, or a member for a multi-member LLC.

The responsible party must supply a Taxpayer Identification Number - an SSN, an ITIN, or an existing EIN. If they have no SSN or ITIN, they can still apply by fax or mail by writing "Foreign" in the SSN/ITIN field, or by phone as an international applicant; see getting an EIN without an SSN. The IRS details the rule on its responsible party page.

Colorado State Tax Registration vs. Federal EIN

A frequent question is whether a Colorado business needs a separate state tax ID in addition to the federal EIN. In most cases, Colorado uses your federal EIN, but the Colorado Department of Revenue (DoR) also assigns a Colorado Account Number (CAN) when you register for state tax accounts.

• Colorado Department of Revenue (DoR): The DoR administers state income tax, sales and use tax, and wage withholding. When you register a sales tax license or a withholding account, the DoR ties it to your federal EIN and issues a Colorado Account Number for filing. Register through the DoR sales tax license page or Revenue Online.
• Wage withholding: Employers paying Colorado wages must open a wage withholding account with the DoR, again using the federal EIN.
• Colorado Department of Labor and Employment (CDLE): Employers also register for unemployment insurance premiums with the CDLE, which likewise uses your EIN.
• Colorado Secretary of State: Entity registration (forming an LLC or corporation) happens with the Secretary of State, but that office does not issue tax IDs - the EIN still comes from the IRS.

The state's one-stop portal, MyBizColorado, lets you register with multiple Colorado agencies at once after you have your EIN. For how these state taxes work, see Colorado LLC tax filing, Colorado self-employment tax, and the national business tax overview.

Common Issues and Tips for EIN Applications

• One EIN per responsible party per day: The online system enforces a daily limit. If you manage several entities, apply on separate days.
• Applicants without an SSN or ITIN: The responsible party cannot use the online tool. Apply by fax or mail with "Foreign" in the SSN/ITIN field, or by phone if international.
• Third-party designee: An accountant or attorney applying for you must be authorized as a third-party designee on Form SS-4, or hold a valid Power of Attorney (Form 2848). See the IRS third-party designee guidance.
• Lost EIN: Find it on prior tax returns or IRS notices, or call the IRS Business & Specialty Tax Line at 800-829-4933.
• Closing an account: An EIN is never reassigned or canceled, but you can close the business account by mailing the IRS a letter; see how to cancel an EIN.

Once you have the EIN, keep the confirmation letter with your records and use the same number consistently across your IRS filings, Colorado Department of Revenue accounts, and bank paperwork. For related steps, browse the glossary or the Colorado LLC formation guide.

Frequently Asked Questions

How do I get an EIN for my Colorado business?

Apply directly with the IRS. The fastest method is online through the IRS EIN Assistant, which issues the number immediately. You can also apply by fax or mail using Form SS-4. The EIN is always free.

Is an EIN required for a Colorado LLC?

Yes, if your Colorado LLC has more than one member, has employees, or elects corporate or S-corporation taxation. Even single-member LLCs commonly need an EIN to open a business bank account or register for a Colorado sales tax license.

What information do I need to apply for an EIN?

You need the legal name and mailing address of your business, the entity type, the reason for applying, and the name and Taxpayer Identification Number (SSN, ITIN, or existing EIN) of the responsible party.

How long does it take to get an EIN in Colorado?

Applying online through the IRS EIN Assistant gives you the EIN immediately. Fax applications take about four business days, and mailed Form SS-4 applications can take four to six weeks.

Do I need a Colorado state tax ID number?

Colorado businesses use their federal EIN with the Colorado Department of Revenue, which issues a Colorado Account Number when you register for a sales tax license or wage withholding. You can register through MyBizColorado or Revenue Online.

Can I get an EIN without an SSN?

Yes. If the responsible party has no SSN, they can use an ITIN. If they have neither, they cannot use the online tool and must apply by fax or mail, writing 'Foreign' in the SSN/ITIN field, or by phone for international applicants.

Related

• How to get an EIN (cluster hub)
• How to form an LLC in Colorado
• What is an ITIN?
• Business tax overview
• How to get an EIN in California (sibling)
• Is an EIN really free?

Sources

1. IRS - Employer ID Numbers (EINs).
2. IRS - How to Apply for an EIN.
3. IRS - Form SS-4, Application for Employer Identification Number (PDF).
4. IRS - Where to File Form SS-4 (Colorado fax and mailing addresses).
5. IRS - Apply for an EIN Online.
6. IRS - Do You Need an EIN?.
7. IRS - Applying for an EIN by Fax.
8. IRS - Applying for an EIN by Mail.
9. IRS - Third Party Designee Authorization.
10. IRS - Taxpayer Identification Numbers (TIN) (SSN, ITIN, EIN).
11. IRS - What Is a Responsible Party?.
12. IRS - How to Cancel an EIN.
13. Colorado Department of Revenue - Sales Tax License (Colorado Account Number, registration).
14. Colorado Department of Revenue - Wage Withholding Tax (employer withholding account).
15. Colorado Department of Labor and Employment - Unemployment Insurance for Employers.
16. Colorado Secretary of State - Business Services (entity registration).

LegalGlass provides general information for educational purposes and is not a law firm or a substitute for advice from a licensed attorney or tax professional. Laws, fees, and thresholds change; verify current requirements with the IRS and Colorado state agencies before acting.