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SOS ID

An SOS ID is a state registry number used to identify a business record. The exact name and meaning of that number depend on the state.

An SOS ID is a number used by a Secretary of State or similar filing office to identify a business record. It is not a nationwide standard. North Carolina, for example, calls its entity-level number the Secretary of State Identification Number, or SOSID.

Do not assume that SOS ID, Entity ID, File Number, Filing Number, Document Number, and Charter Number always mean the same thing. A state may use one of these labels for the business itself and another for a document filed for that business.

How State Labels Differ

  • North Carolina uses SOSID for the business entity.
  • Maine uses Charter Number as the unique and constant identifier for an entity.
  • Delaware uses File Number as the unique identifier for an entity.
  • Florida assigns a Document Number to the entity.
  • Colorado keeps an entity ID and a filed document’s document number separate.
  • Massachusetts keeps an entity identification number and filing numbers separate.

The same label can therefore perform different jobs in different systems. Always use the exact label shown in the official state registry or filing form.

What Is an SOS ID Used For?

When a state uses SOS ID as its entity-level identifier, the number helps the filing office and the public find the correct business record. A form may ask for it when a business files a report, orders a certificate, or changes registry information.

Other agencies may use a separate tax, account, license, or employer number. Follow the label on the official form instead of substituting a number that looks similar.

How to Find Your SOS ID

  1. Open the state’s official business registry.
  2. Search for the legal business name.
  3. Open the full business record.
  4. Copy the number with its exact label.
  5. If the record also lists filing or document numbers, do not assume they identify the business itself.

Some registries display the entity number publicly. Others may require you to open a detail page or review an accepted filing. If a form asks for a number you cannot identify, use the filing agency’s instructions or contact that agency.

SOS ID vs. Federal Tax ID (EIN)

A state registry number is not an Employer Identification Number. An EIN is issued by the IRS for federal tax purposes. Do not enter an EIN in a state registry ID field unless the official form specifically asks for it.

Sources Reviewed

The official sources below were retrieved and confirmed on August 20, 2026.