USA company registration number: Essential guide for founders

Key differences between Employer Identification Number and State Entity Number

The Employer Identification Number and State Entity Number are two different identifiers for the same business. However, these two numbers work separately for separate purposes, like:

The EIN remains constant regardless where you expand in the US. The state registration number, however, varies from state to state. So, you need a new state registration number if you decide to expand into another US state.

If you register as a foreign entity in another state, you will receive a different state entity number there. The IRS recognizes only the EIN and not the state-issued entity ID.

The Employer Identification Number (EIN)

Your EIN is the closest thing the USA has to a universal business identifier. It's a 9-digit number assigned by the Internal Revenue Service (IRS), formatted as XX-XXXXXXX.

The EIN tracks federal taxes and payroll obligations. You'll need it to open a business bank account, apply for business loans, hire employees, and file federal tax returns. It works similarly to a Social Security Number. Most financial institutions and government agencies will ask for it.

How to obtain an EIN

To obtain an EIN, your company needs to be eligible for a federal tax ID number. The IRS determines your company’s eligibility before issuing your employee identification number. The IRS offers three methods to get an EIN, each with different processing times:

• Online application: Fill out and submit your EIN application on the IRS website to get your EIN immediately. However, you need to fill out the form in one session. You can fill out the form only once a day.
• Fax application: Download Form SS-4, fill it out, and fax it to the IRS. You may receive your EIN number within a week.
• Mail application: You can also send your completed Form SS-4 to the IRS via postal mail. However, this method takes the longest, about 4-5 weeks, to receive your EIN.

Make sure that your company information in Form SS-4 is accurate to avoid any discrepancies later. If you've already applied, you should have received a confirmation letter (Form CP 575) from the IRS with your EIN clearly stated. Keep this document accessible—you'll reference it constantly.

State registration numbers & company IDs

When you register your startup in any USA state, the state government automatically issues an entity ID, or the State Registration Number. This number signifies that your startup is compliant with the state’s business laws. Every U.S. state maintains its own business registry. When you file your Articles of Incorporation (for corporations) or Articles of Organization (for LLCs), the state assigns you a unique identifier.

This US Business Registration Number (BRN) goes by different names depending on where you're registered. Some states call it a Company ID (CID), others use terms like Entity Number, Charter Number, or File Number. For example, a business incorporated in Texas will have a Texas File Number, while one in Washington will have a Washington UBI (Unified Business Identifier). The format and length vary by state. Some are purely numeric, others include letters. There's no standardization across the country.

Some states require an additional state-level EIN for payroll taxes, sales tax, or other state-specific obligations. Michigan, for instance, issues its own state employer identification number separate from the federal EIN. Check your state's Department of Revenue or Taxation website to confirm what's required.

Your state registration number proves your business legally exists in that jurisdiction. You'll need it for state tax filings, annual reports, and any legal documents filed within that state. If you're expanding to multiple states, you'll have a different registration number in each one.

Specialized identifiers and when you need them

For different industries and business structures, you may need additional identifiers beyond the EIN and state registration number.

How to find a USA company registration number

Whether you're looking up your own business or researching another company, here's how to locate the right identifiers.

Searching for your own business

Both your EIN and State Registration Numbers appear on different documents that are available to you as soon as your business is registered with the federal and state agencies.

• Check your IRS EIN confirmation letter (Form CP 575): If you apply online, you will receive the confirmation letter immediately. If you apply by fax or mail, the IRS mails it to your business address.
• Review your business tax returns: Your EIN appears on every federal tax return you've filed, including Form 1120 (C-corporations), Form 1120-S (S-corporations), or Form 1065 (partnership firms).
• Look at your original Articles of Incorporation or Organization: When you register your business with the state, you receive a filed copy of your formation documents. The state registration number appears on this document, usually in the top corner or footer.
• Check annual report confirmations: If you've filed annual reports with your state, the confirmation emails or letters include your state registration number.

Searching for another business

Since you are looking for another company’s registered company number in the USA, the process to find it differs. The USA has several online government databases for such information.

• Public companies: Use the SEC EDGAR database and search by company name to find the CIK and access all public filings. This database includes detailed financial information, ownership structures, and corporate governance documents.
• Private companies: Navigate to the Secretary of State website for the state where the company is registered. Most states offer a free business entity search tool. You'll need the exact legal name of the business or the name of a registered agent. The search results typically display the company's registration number, formation date, status (active or dissolved), and registered agent information.
• Non-profits: Use the IRS Tax-Exempt Organization Search tool to verify non-profit status and find the EIN. This database includes all organizations recognized as tax-exempt under Section 501(c) of the Internal Revenue Code.
• Third-party databases: Tools like OpenCorporates aggregate business registration data from 50+ jurisdictions worldwide, including all U.S. states. These platforms offer a simple search interface, making it easier to find companies when you're unsure which state they're registered in.

If a company operates in multiple states, it will have a "home state" where it's incorporated. Alongside, it may also have foreign qualification numbers in other states where it operates. You may need to search multiple Secretary of State databases to get the complete picture.

Why accurate IDs matter for your business strategy

These numbers are the foundation of your business's legal and financial infrastructure.

Legitimacy and Know Your Business (KYB) verification

When you're applying for a business bank account, setting up a payment processor, or partnering with another company, they'll verify your business using these identifiers. Accurate registration numbers prove you're a legitimate entity and establish trust. Financial institutions use them to perform compliance checks.

Financial capability

An EIN is mandatory to open a business bank account in the USA. It is necessary when you want to hire employees. If you are applying for business credit, you need an EIN. You require your state registration number for any legal contracts, real estate transactions, or state-level licenses. Without these identifiers, your business cannot function commercially.

Compliance and reporting

Tax authorities, regulators, and licensing boards use these numbers to track your filings and ensure compliance. If you change your business address, legal structure, or ownership, you need to update your records with both the IRS and your state. Having this information ensures that you address tax notices timely, keep your business status active, and uphold good standing.

Scaling across borders

If you're expanding internationally or working with global partners, accurate business identifiers become even more critical. International banks, payment processors, and regulatory authorities will request your EIN and state registration details to verify your USA  business entity. Having these numbers readily available simplifies cross-border transactions and banking relationships.

Final Thoughts

The US gives different company registration numbers for separate purposes. A combination of federal EIN and state registration number contributes to creating a complete identity of your business. Your EIN connects your federal obligations, while state registration numbers show compliance with local laws. Keep both numbers easily accessible along with your formation documents, EIN confirmation letter, and any licenses or permits.

When you scale your business, these documents become necessary for every bank application, vendor agreement, tax filing, and compliance requirement. Your company registration numbers are proof of your business's legitimacy, creating a strong base for your company’s market reputation.

Similarly, find your potential business partner’s or vendor’s business registration number to ensure business transparency and trust. With this information, expand your business with confidence.