To find your business registration number, start with the state where the company was formed: every state runs a free online business entity search through the secretary of state’s office, and the results page displays the state-assigned entity number along with formation date, status, and registered agent. That covers state registration. If you actually need the federal Employer Identification Number (EIN), the search works differently, because the IRS does not publish a general EIN directory. Most businesses carry both numbers, and figuring out which one you need is the difference between a two-minute search and an afternoon of dead ends.
Which Number You Actually Need
Three different identifiers get called “business registration numbers” in everyday use, and they live in three different databases.
- The Employer Identification Number (EIN) is a nine-digit federal tax ID in the format XX-XXXXXXX, issued by the IRS. Every corporation, partnership, and LLC has one. Sole proprietors can usually use their Social Security number instead unless they have employees, maintain a retirement plan, or file excise tax returns.1eCFR. 26 CFR 301.6109-1 – Identifying Numbers
- The state entity number is an alphanumeric code the state filing office assigns when it accepts your formation documents. It proves the company legally exists in that state and appears on annual reports, state tax filings, and court paperwork.
- The Unique Entity Identifier (UEI) is a 12-digit number issued through SAM.gov. It replaced the old DUNS number for federal contracting and grants, and only businesses working with the federal government need one.2GSA. Unique Entity ID is Here
Match the number to what you’re doing. Verifying that a company legally exists, or naming it in a lawsuit? You need the state entity number. Issuing a 1099 or reporting payments? You need the EIN. Checking a federal contractor’s credentials? UEI.
Check Your Own Paperwork First
If the business is yours, the fastest search is the file cabinet.
Your articles of incorporation or articles of organization are the filings that brought the company into legal existence, and the state filing office stamps or prints the assigned entity number on the accepted copy, usually near the top of the first page. Lost the originals? Most states let you download copies from their online portal or order certified copies by mail.
For the EIN, dig up the CP 575 confirmation notice the IRS mailed when it first assigned the number. If that’s gone, the EIN appears on every federal tax return the business has filed. On Form 1120 corporate returns it sits as Item B in the name and address block at the top of the form.3Internal Revenue Service. Instructions for Form 1120 Partnership returns (Form 1065) and S-corp returns (Form 1120-S) use the same layout.
Nothing on file at all? Call the IRS Business and Specialty Tax line at 1-800-829-4933 and request a 147C verification letter. After verifying your identity, the IRS will confirm your EIN and either fax or mail the letter. Only an authorized person for the business (an officer, partner, or sole proprietor) can make the request.
Beyond those, state tax permits, local business licenses, certificates of good standing, and bank account opening packets typically list one or both numbers. Business licenses are often posted at the premises, which makes them the easiest visual reference.
Searching a State Business Registry
Every state maintains a public database of registered entities, and nearly all of them offer free online search. Businesses generally register with the secretary of state or an equivalent agency, and that same office hosts the searchable registry.4U.S. Small Business Administration. Register Your Business
Go to the secretary of state website for the state where the business was formed and look for a link labeled “business search,” “entity search,” or “business filings.” Enter the company’s legal name, not a brand name. Include the entity suffix (LLC, Inc., Corp.) if you know it, because the legal name on file includes it. Spelling variations and missing punctuation throw off exact-match searches, so try a partial name if nothing appears.
Most portals let you filter by entity status (active, dissolved, withdrawn) and entity type. When you find the right match, the detail page shows the state-assigned entity number, registered agent, formation date, and filing history. Many states also let you download the original formation documents as PDFs from that page.
When the Legal Name Isn’t the Brand Name
A company customers know as “Sunrise Coffee” might be registered as “Sunrise Hospitality Group LLC.” A DBA (doing business as) or trade name is separate from the entity name on file with the state, and multiple businesses can share the same DBA within a state.5U.S. Small Business Administration. Choose Your Business Name If you only know the DBA, search the state’s assumed name or fictitious name records first to surface the underlying legal entity, then search that entity name for the registration number.
Knowing the registered agent, a principal officer’s name, or the city of the principal office can also narrow generic results. Some state portals support officer and agent name searches directly.
Businesses Registered in More Than One State
A company formed in Delaware but operating in Texas will have a registration number in both states. The Delaware number is the domestic registration; the Texas number is a foreign qualification. If you’re dealing with the company in Texas, you may need the Texas-issued number for local filings even though the original formation happened elsewhere. Search the state where you’re actually doing business, not just the state of incorporation.
Finding Someone Else’s EIN
EINs are harder to look up for a business that isn’t yours, because the IRS runs no general public directory. What’s available depends on the type of entity.
Tax-exempt organizations. The IRS Tax Exempt Organization Search at apps.irs.gov lets you look up any nonprofit’s EIN for free.6Internal Revenue Service. Tax Exempt Organization Search Search by organization name to view Form 990 returns, determination letters, and revocation data. The EIN appears on every 990 filing. This is the most reliable way to find a nonprofit’s federal ID.
Publicly traded companies. Public companies file annual reports (10-K) and quarterly reports (10-Q) with the SEC, and those filings include the EIN. Search the SEC’s EDGAR database by company name, then look for the EIN on the cover page of any 10-K or 10-Q.7U.S. Securities and Exchange Commission. Look Up a Central Index Key (CIK) Number
Private for-profit companies. No free government lookup exists. Ask the company directly, since businesses routinely share their EIN on a W-9 when you’re a vendor or contractor, or check any 1099 or other tax document they’ve already issued to you. If a company won’t provide its EIN and you need it for tax reporting, the IRS allows you to withhold 24% of payments as backup withholding until the correct taxpayer identification number is provided.
Federal Contractors and SAM.gov
If a business holds federal contracts or receives federal grants, its Unique Entity Identifier is publicly searchable on SAM.gov. You can search by legal business name, CAGE code, or UEI.2GSA. Unique Entity ID is Here The SAM.gov registration process cross-references the company’s EIN with IRS records, so the data tends to be accurate and current.8EXIM.GOV. SAM.GOV and Unique Entity Identifier (UEI) Requirements
Not every business has a UEI. Only those seeking federal financial assistance, government contracts, or certain federal programs are required to register. For the businesses that do, SAM.gov is one of the most complete public sources available.
When an Old Number No Longer Works
Registration numbers are not always permanent, and certain structural changes force a business to get an entirely new identifier. If you’re searching with a number that used to work, restructuring may be the reason it doesn’t now.
The IRS requires a new EIN when a business changes ownership or structure in specific ways. Simply changing the business name or address does not trigger a new EIN. These changes do:9Internal Revenue Service. When to Get a New EIN
- Sole proprietors who incorporate, form a partnership, or declare bankruptcy.
- Corporations that receive a new charter from the secretary of state, convert to a partnership or sole proprietorship, or merge to create a new corporation.
- Partnerships that incorporate, dissolve and start a new partnership, or where one partner takes over as a sole proprietor.
- LLCs that terminate and reform as a corporation or partnership.
State rules vary. Converting from one entity type to another, say from an LLC to a corporation, often results in a new state registration number. Some states allow statutory conversions that preserve the same entity number; others treat the conversion as a dissolution and new formation. If a company recently restructured, search for both the old and new entity names to trace the full filing history.
Why the Right Number Matters
Using the wrong identifier on an official filing is more than an inconvenience. The IRS charges penalties for filing information returns like 1099s with an incorrect taxpayer identification number. For returns due in 2026, the penalty starts at $60 per incorrect return if corrected within 30 days, jumps to $130 if corrected by August 1, and reaches $340 per return after that. Intentional disregard pushes the penalty to $680 per return.10Internal Revenue Service. Information Return Penalties
At the state level, filing court documents or government forms with an incorrect entity number can cause rejections, delays, or dismissal of legal actions. If you sue a business using a stale registration number from before a merger, the filing may not be legally effective against the intended company. Confirm the number is current before you rely on it.