What is a business registration number?

A business registration number is the identifier a US Secretary of State assigns a company when it registers in that state. Each state issues its own, in its own format, and the number is unique only within that state. There is no national registration number, and it is not the same as the federal EIN.

What does a business registration number identify?

When a company files to form or register in a state, that state's business registry gives it a number. The number identifies the entity's record inside that one state's system, and nothing more. It is assigned at registration and stays with the entity for the life of its filing.

Every state names it differently. California calls it an entity number, Delaware and Illinois a file number, Florida a document number, Georgia a control number, and Washington a UBI, short for Unified Business Identifier. They all do the same job: point to one record in one state's database. None of them is a national ID, and none is the company's tax number.

The practical consequence is the one most sources miss. A registration number on its own does not tell you which company it belongs to, because it only means something paired with the state that issued it. To resolve a number, you need to know its state first.

Is a business registration number unique?

Within its own state, yes. A state never issues the same number to two entities, so a registration number plus its state identifies exactly one company. Across states, no. Each Secretary of State assigns numbers independently, starting from its own sequence, so the same number turns up again and again in different states.

The overlap is large. Among the 92,347,458 business-entity records on file across all 50 registries, there are 76,187,929 distinct registration numbers. At least 10,092,747 of those numbers are used by companies in more than one state, and at least 26,252,276 entities, more than one in four, share their registration number with a company in another state. The busiest single number is held by companies in 12 different states.

A worked example makes the collision concrete. Registration number 1013010 belongs to ten unrelated entities across ten states:

These counts cover the records on file across all 50 registries, as of July 2026, and measure how many states each registration number appears in. A state does not reuse a number, so every number that shows up in two states is a real collision, which makes the totals floors rather than estimates. The takeaway for anyone handling these numbers: a registration number is not a key you can dedupe or join on across states. Two rows with the same number are usually two different companies.

Why does every state's number look different?

Because each registry designed its own scheme, and they never coordinated. Some states use plain sequential integers. Others prefix a letter, pad with zeros, insert spaces, or encode the entity type. Of the 50 registries, 27 put letters in at least some of their numbers, and 5 write them with spaces.

Illinois is the clearest case of a scheme carrying meaning: it prefixes corporations with CORP and LLCs with LLC, so the number itself tells you the entity type. Its registry holds 1,948,258 numbers on the CORP pattern and 1,400,517 on the LLC pattern. Washington writes its UBI in three spaced groups. California fronts corporation numbers with a C. The format can sometimes hint at the state, but it is not reliable enough to identify one, because several states share the plain-integer pattern.

Is a business registration number the same as an EIN?

No, and the two are the most commonly confused identifiers in US business data. An EIN, or Employer Identification Number, is the federal tax ID the IRS issues to a business. It is nine digits, written as XX-XXXXXXX, one per business, and unique across the whole country. A registration number is issued by a state, at formation, and is unique only inside that state.

The last row is where the two identifiers diverge most. A company has a single EIN no matter how far it expands. But when it operates beyond its home state, it registers as a foreign entity in each additional state and receives a new registration number there. A business active in ten states can hold ten registration numbers and one EIN.

How do you look up a company by its registration number?

Start by identifying the state. Because the same number exists in many states, the number alone is ambiguous, so a lookup begins with the issuing state and then queries that state's registry.

• If you know the state, search its Secretary of State business database directly. Every state runs a free public search, usually by entity name or number.
• If the company is publicly traded, the SEC's EDGAR system indexes its filings nationally and is searchable by name without knowing the state.
• If you do not know the state, an aggregator or a directory of registries is the starting point. The National Association of Secretaries of State maintains links to every state's business search, and open databases like OpenCorporates index many states at once.

Knowing the number belongs to a specific state is also the first step in verifying an entity against official records, and in tracing who owns or runs it from what the state publishes.

Resolving a number to a company across states

Because a registration number means nothing without its state, resolving one at scale means addressing the right registry every time. GovFiles normalizes all 50 state registries into one schema, and looks up an entity by its jurisdiction code plus its registration number, so the same number resolves to the right company in each state. The requests below, verified against the docs at docs.govfiles.dev, show the number 1013010 returning two different companies:

# Number 1013010 in Delaware
curl -H "X-API-Key: $KEY" \
  "https://api.govfiles.dev/v2/companies/us_de/1013010"
# -> "legal_name": "DIGITAL EQUIPMENT CORPORATION"

# The same number in New York
curl -H "X-API-Key: $KEY" \
  "https://api.govfiles.dev/v2/companies/us_ny/1013010"
# -> "legal_name": "SHRIMP O RAMA, INC."

The jurisdiction code, us_de or us_ny, is the part the number cannot supply on its own. Pair it with the registration number and you have a key that identifies one company. Drop it and you have a number that a dozen companies might answer to.

Frequently asked

What is a business registration number? It is the identifier a US Secretary of State assigns a company when it registers in that state. States call it a file number, entity number, charter number, control number, or UBI. It identifies the entity within that one state's system. It is not a federal number, and it is not the same as an EIN.

Can two companies have the same registration number? Yes, in two different states. Each state assigns its own numbers independently, so the same number is often held by unrelated companies in other states. In the records on file across all 50 registries, at least 26 million entities share their registration number with a company in another state. Within a single state, the number is unique.

Is a business registration number the same as an EIN? No. An EIN is a federal tax ID issued by the IRS, nine digits, one per business, unique nationwide. A registration number is issued by a state at formation and is unique only within that state. A company has one EIN but can hold a different registration number in every state where it registers.

Is there a national US business registration number? No. There is no national business registry and no national registration number. Every US company is registered with one or more individual states, each of which issues its own number in its own format. The closest thing to a nationwide business identifier is the federal EIN, which is a tax ID, not a registration number.