employer identification number
Reviewed by Owen Hathaway, AttorneyUpdated June 4, 2026The IRS's nine-digit tax ID for an entity that is not an individual, such as a business, trust, or estate. It works like a Social Security number for that entity: used to open accounts and file returns.
An employer identification number (EIN) is a nine-digit identifier the IRS assigns to an entity for tax purposes, the equivalent of a Social Security number for something that is not an individual. Despite the name, it reaches well beyond employers: the IRS uses the EIN as the taxpayer identification number for almost any non-natural person, including businesses, trusts, and estates.
Businesses are the original and most common users. Most LLCs, corporations, partnerships, and nonprofits need an EIN to open bank accounts, hire and pay employees, file returns, and establish the entity's separate identity. It can be obtained directly from the IRS at no cost, and for a business it also reinforces the separateness that supports the liability shield.
Estate planning relies on EINs too. An irrevocable trust generally needs its own EIN. A revocable living trust normally uses the grantor's Social Security number while the grantor is alive, then obtains an EIN once it becomes irrevocable, usually at the grantor's death. A probate estate likewise gets its own EIN, which the personal representative uses to open the estate's accounts and file its fiduciary income tax return (Form 1041).
An EIN is federal and applies the same in Colorado and Wyoming. It is separate from any state tax account an entity may need to register for, such as a Colorado sales tax license.
Related terms
- limited liability companyA business structure that shields its owners' personal assets from the company's debts and lawsuits, while staying simpler and more flexible to run than a corporation.
- S corporation electionA tax election that lets a corporation or LLC pass income through to owners (avoiding double taxation) while potentially reducing self-employment tax. It is not a separate kind of entity.
- articles of organizationThe formation document filed with the state that legally creates an LLC. (Corporations and nonprofits file articles of incorporation instead.)