Company Identifiers: Types, Lookups, and How to Use Them

For two years, one customer lived in my CRM under four different names. “Acme Corp.” “Acme Corporation.” “ACME Inc.” “Acme, LLC.”

My team treated them as four accounts. Four owners. Four forecasts. One very confused customer.

And the fix wasn’t a better naming rule. It was a company identifier, a stable code that says “these are all the same legal entity” no matter how someone typed the name. The day we started matching on identifiers instead of names, our duplicate rate dropped hard. Our reporting finally made sense.

So let me walk you through it. What company identifiers are, the main types you’ll actually meet, where to look them up, and how to use them so your data stops lying to you. Let’s get into it. 👇

📌 TL;DR: A company identifier is a unique code that pins a business to one legal entity. Think of an EIN (US tax), an LEI (global finance), a D-U-N-S Number (business credit), a VAT number (EU tax), or a company registration number. Names are messy and change; identifiers don't. Match and dedupe your records on identifiers, not names, and your CRM, compliance, and reporting all get more honest at once.

What is a company identifier?

A company identifier is a unique code assigned to a business so systems can recognize it consistently, whatever the name spelling. It’s the difference between guessing and knowing.

Names betray you constantly. Companies rebrand, get acquired, add “Inc.” or drop it, or share a name with ten unrelated firms. An identifier cuts through all of that. It’s assigned by an authority (a government, a standards body, or a data provider), and it points to exactly one entity.

Here’s the mental model I use → a name is what you call a company; an identifier is who the company actually IS. You can have many names for one identifier, but never one identifier for two companies. That’s the whole reason these codes exist.

The main types of company identifiers

There’s no single global business ID. Instead, there are several identifiers, each built for a different job. Here are the ones you’ll actually run into, and when each number matters.

Identifier	Issued by	Best for	Scope
EIN (Employer ID Number)	US IRS	US tax, payroll, banking	United States
LEI (Legal Entity Identifier)	GLEIF network	Financial transactions, regulatory reporting	Global
D-U-N-S Number	Dun & Bradstreet	Business credit, procurement	Global
VAT number	National tax authorities	EU / UK trade and tax	Country-specific
CIK / ticker	US SEC / stock exchanges	Public-company filings and markets	Public companies
Company registration number	National registries	Legal existence, incorporation	Country-specific

EIN, the US tax ID

An EIN is a nine-digit number the IRS assigns to US businesses for tax and payroll. It’s formatted like 12-3456789, and most US companies hold exactly one.

You need a new EIN when the legal structure changes, say a sole proprietorship becomes a corporation. The IRS EIN page lays out exactly when a fresh one is required, and applying is free.

LEI, the global finance ID

An LEI is a 20-character code that identifies a legal entity in financial transactions anywhere in the world. After 2008, regulators wanted to trace who was trading with whom, and the LEI became the answer.

It follows the ISO 17442 standard, and every LEI is public and free to look up. GLEIF explains the LEI and its structure, and the GLEIF search index is open to anyone. The formal spec lives in ISO 17442.

D-U-N-S, VAT, registration numbers, and tickers

A D-U-N-S Number is a nine-digit code assigned by Dun & Bradstreet for business credit and procurement. You’ll meet it the day you register as a vendor. A VAT number identifies a business for value-added tax in the EU and UK, and you can confirm any EU one through the official VIES lookup.

A company registration number proves a business legally exists in its home country’s registry, like Companies House in the UK. And for public companies, the SEC assigns a CIK code for filings, while exchanges assign the ticker symbol you see in market data.

One more identifier deserves a seat at this table: the company domain. It’s not assigned by a registry, but it’s unique, it’s easy to capture, and nearly every business has one. For sales and marketing data, a verified domain often works as the most practical everyday company ID, with the formal codes layered on top.

Where to find and look up company identifiers

Most company identifiers are public and free to look up; you just need to know which door to knock on. Here’s where each number lives:

• EIN → on tax filings, payroll docs, or a company’s own W-9. Public companies list it in SEC filings.
• LEI → free in the GLEIF global index, searchable by name or code.
• VAT → on invoices, and verifiable through the EU VIES system.
• Registration number → in the national business registry (Companies House in the UK, state registries in the US).
• D-U-N-S → through Dun & Bradstreet’s lookup, or on procurement records.

The hard part isn’t finding one identifier for one company you already know. It’s connecting thousands of messy records to the right identifiers at scale. That’s a data matching problem, linking your internal record to the correct entity so you don’t attach the wrong company’s tax ID to the wrong account.

And the usual first step is turning a raw company name into a verified domain, because the domain then anchors everything else. That name-to-domain gap is exactly what Company URL Finder was built to close.

How to use identifiers in your data

Use identifiers as the join key, the one field every record matches on, instead of the company name. That single change fixes more data problems than anything else I’ve tried.

When you match on an identifier, four things happen. Duplicates collapse, because deduplication finally has a reliable key. Subsidiaries connect to parents. Compliance checks automate, because you’re verifying a code, not eyeballing a name. And your data quality climbs, because every downstream report inherits a clean, unique spine.

Then data enrichment gets easier too. Once a record carries a solid identifier, appended firmographics (revenue, size, industry, location) land on the right entity every time. Bad match, wrong append. Good identifier, clean append. It’s that direct. Our company data guide walks through those fields one by one.

🔍 The join-key rule: Never make a company name your primary match field. Names duplicate, drift, and collide. Pick the strongest identifier you have for each record (EIN, LEI, or a verified domain) and match on THAT. The name becomes a label for humans, not the thing your systems trust.

Which company identifier should you use?

Pick the identifier that matches your job, not the fanciest one. There’s no universal winner here; the right code depends on what you’re doing.

Doing US tax, payroll, or banking? Use the EIN. Working in financial services or regulatory reporting? The LEI is your standard. Running vendor onboarding or checking business credit? D-U-N-S. Trading across the EU? VAT. And for pure sales and marketing data, where you just need to unify accounts, a verified company domain is usually the most practical everyday key. It’s easy to capture, hard to duplicate, and links cleanly to the formal codes above.

So I keep a small hierarchy in my head → domain for everyday matching, then EIN or LEI when a record needs legal or financial precision. Start with what you can reliably capture. Layer the authoritative IDs on top as the stakes rise. And if you’re rolling identifiers into broader research, our company analysis walkthrough shows where they fit.

Common mistakes with company identifiers

The most common mistake is matching records on company names when a real identifier was available. But it’s not the only one. Here’s what I see over and over:

• Storing identifiers as numbers. Spreadsheets strip leading zeros, and a mangled ID matches nothing. Store every identifier as text.
• Assuming one ID type covers every country. An EIN means nothing in Germany. Global lists need a global code (LEI, D-U-N-S) or the domain.
• Never validating the format. A wrong identifier is worse than a missing one, because it poisons the match quietly.
• Attaching an ID to the wrong entity in a corporate family. The subsidiary and the parent are different legal entities with different codes. Match at the level your use case needs.
• Trusting the string without the registry. For codes that support it, like the LEI, verify against the issuing registry, not just the pattern.

💡 Format check: An EIN is nine digits (12-3456789). An LEI is 20 alphanumeric characters with a built-in checksum you can validate mathematically. VAT numbers follow a country prefix plus a national pattern. A ten-second shape check catches typos before they break a match.

The cleanup that taught me this

Back in my Hamburg agency days, around 2019, I inherited a CRM with about 12,000 company records. We deduped it by name. Twice. Both times the duplicates crept back within a quarter, because every import spelled names its own way.

The third attempt, we did it differently. We resolved every record to a verified domain first, added registration numbers for the accounts that touched invoicing, and made the domain the match key. The 12,000 rows collapsed to roughly 9,400 real companies. And the duplicates didn’t come back, because the key didn’t drift.

That’s how I know this works: years of cleaning B2B lists, not theory. One honest caveat, though. Registries, formats, and lookup tools change over time. So when a decision rides on an identifier, verify it at the issuing source (IRS, GLEIF, VIES, your national registry), not in a blog post. Including this one.

Frequently Asked Questions

What is a company identifier?

A company identifier is a unique code assigned to a business by an authority so systems can recognize the same entity consistently. Common examples include the EIN for US tax, the LEI for global finance, and the D-U-N-S Number for business credit. Identifiers stay stable even when a company rebrands or gets acquired.

What is an example of a company identifier?

An EIN like 12-3456789 is a classic example: a nine-digit code the IRS assigns to one US business. Other examples include a 20-character LEI, a nine-digit D-U-N-S Number, a VAT number like DE123456789, and a UK company registration number from Companies House.

Where can I find my company identifier?

Check public sources first: the GLEIF index for LEIs, national registries for registration numbers, and the EU VIES tool for VAT numbers. A US company’s EIN often appears on its SEC filings or W-9. For matching many companies at once, you map records to the right entities programmatically rather than one by one.

What is the difference between an EIN, an LEI, and a D-U-N-S Number?

An EIN is a US tax ID from the IRS, an LEI is a global financial-transaction ID from the GLEIF network, and a D-U-N-S Number is a business-credit ID from Dun & Bradstreet. They serve different jobs, so a single company can hold all three at once. Pick the one that fits your use case: tax, finance, or credit.

Is a company identifier the same as a tax ID?

Not exactly: a tax ID like an EIN or VAT number is one type of company identifier, but not all identifiers are tax-related. An LEI and a D-U-N-S Number identify a company without being tax numbers. So “tax ID” is a subset of the broader identifier family.

How can I look up a company’s EIN?

For public companies, search their SEC filings, where the EIN appears on documents like the 10-K. For private companies, the EIN may be on a shared W-9, a business license, or paperwork you already exchange. There’s no universal free public EIN directory, so verified filings are your best source.

Why should I match records on identifiers instead of names?

Because names duplicate, drift, and collide, while identifiers point to exactly one legal entity. Matching on a name creates duplicate accounts and broken reports. Matching on an identifier collapses duplicates and lets enrichment land on the correct company every time.

References

• IRS: Employer Identification Number, the official EIN rules and application.
• GLEIF: Introducing the LEI, structure and purpose of the Legal Entity Identifier.
• ISO 17442, the formal LEI standard.
• European Commission VIES, the official EU VAT number validation tool.
• SEC EDGAR filing search, where public-company CIKs and EINs surface.
• UK Companies House, the national registry behind UK registration numbers.

It’s time to give your data one spine

Pick a primary identifier this week, even if it’s just the domain. Backfill it across your records. Then make it the match key everywhere.

Your duplicates will collapse, your reports will agree with each other, and “which Acme is this?” stops being a meeting. You’ve got this.

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