What Is an Agency ID? EINs, State IDs, and the UEI

An agency ID for a business is any identification number a government agency assigns to tie your company to a specific obligation, such as paying federal taxes, withholding payroll, collecting sales tax, or bidding on federal contracts. The most common one is the Employer Identification Number (EIN) from the IRS, but depending on what you sell, whether you have employees, and where you operate, you may also need state tax IDs, a state unemployment insurance number, local business licenses, and a Unique Entity Identifier for federal work. Each number answers to a different agency, and missing one can block you from hiring, opening a bank account, or filing a return.

The Federal EIN

The EIN is the foundational ID for most U.S. businesses. It’s a nine-digit number the IRS assigns in the format XX-XXXXXXX, and it works like a Social Security Number for your company. The IRS uses it to match your business to every tax return, information filing, and third-party income report tied to your entity.¹

You need an EIN if your business is a corporation, partnership, or multi-member LLC. You also need one if you have employees, pay excise taxes, or withhold taxes on payments to nonresident aliens. Trusts, estates, and tax-exempt organizations need their own EINs as well.²

Beyond tax filings, the EIN is what banks ask for when you open a commercial checking or savings account, and it’s required to set up a tax-advantaged retirement plan like a SEP IRA or 401(k). Even if you don’t technically need one for federal tax purposes, you can request an EIN for banking or state tax registration.²

Sole Proprietors and Single-Member LLCs

Not every business needs an EIN right away. If you run a single-member LLC that’s treated as a disregarded entity for tax purposes and you have no employees or excise tax liability, you can use your own Social Security Number on tax filings instead.³ The same goes for sole proprietors operating under their own legal name, who can also open a business bank account using their SSN.⁴

Hire one employee, and the rules change. You’ll need an EIN to handle payroll tax reporting and withholding, and a single-member LLC with employees must use its own name and EIN for employment tax purposes.³ Many sole proprietors get an EIN even before that point, to keep their SSN off invoices and other business paperwork.

Foreign nationals without an SSN who need to file U.S. tax returns can use an Individual Taxpayer Identification Number (ITIN) as the responsible party’s ID when applying for an EIN. The ITIN itself is only for federal tax purposes and, per the IRS, is not issued solely to start a business or open a bank account.⁵

When You Need a New EIN

An EIN is permanently tied to the entity it was assigned to, but certain structural changes retire the old number and require a fresh application. The general rule: if you change ownership or entity structure, expect to apply again.⁶

Sole proprietors need a new EIN when they incorporate, form a partnership, or declare bankruptcy.
Corporations need one after receiving a new charter from the secretary of state, converting to a partnership or sole proprietorship, or merging into a new corporation.
Partnerships need one when they incorporate, when a single partner takes over as a sole proprietor, or when they dissolve and start over.
LLCs need one when they terminate and re-form as a corporation or partnership, and single-member LLCs need one when they first take on excise or employment tax obligations.

A sole proprietor who incorporates sometimes keeps filing under the old EIN for months before catching the mismatch. The IRS won’t necessarily reject those filings immediately, but it creates a mess that gets harder to untangle the longer it runs.⁶

How to Apply for an EIN

Applying online through the IRS website is the fastest route. You answer questions about your entity type, provide the responsible party’s name and taxpayer identification number (SSN or ITIN), and receive your EIN at the end of the session. The online system is open to businesses whose principal office is in the United States or U.S. territories.⁷

If you can’t use the online system, submit a completed Form SS-4 by fax and expect your EIN within about four business days, or by mail and wait roughly four to five weeks. International applicants whose principal business is outside the United States can apply by phone at 267-941-1099.⁷

Pick one method per entity. Filing by both fax and mail can result in duplicate EINs, which creates its own problems. Store the number with your formation documents once you have it.

Skip the third-party filing sites. Dozens of websites advertise “fast EIN filing” and charge anywhere from $50 to $300 for what the IRS provides at no cost. The FTC has sent warning letters to operators of these sites, noting that they often fail to disclose their entire fee is a service charge for something you can do yourself on irs.gov.⁸ If the URL doesn’t end in .gov, you’re paying a middleman.

State and Local IDs Your EIN Doesn’t Replace

Your federal EIN is the starting point, not the finish line. State and local governments run their own registration systems, and each assigns its own ID tied to a specific obligation.

Sales Tax Permits

If your business sells taxable goods or services, you’ll need to register with the state’s revenue department for a sales tax permit, sometimes called a seller’s permit. That registration is what authorizes you to collect sales tax from customers and remit it. Most states don’t charge for the permit itself, though some require a security deposit. A business with physical locations or other taxable connections in multiple states needs a separate registration in each.

State Unemployment Insurance Numbers

Any business with employees must register with the state workforce agency for a State Unemployment Insurance (SUI) number, which is used to report and pay state unemployment taxes. Rates and taxable wage bases vary significantly by state.

Federal unemployment tax runs parallel. Employers owe FUTA at 6.0% on the first $7,000 paid to each employee per year, though most receive a credit for state unemployment taxes paid that effectively reduces the federal rate to 0.6% in practice.⁹

Professional Licenses and Local Business Receipts

Regulated fields like healthcare, law, and construction usually require professional licensing IDs from the relevant state board to confirm practitioners meet education and competency standards. At the county or municipal level, many jurisdictions require a separate business tax receipt or occupational license to operate within their boundaries. Fees range widely, from under $50 to several hundred dollars depending on the jurisdiction and industry.

The Unique Entity Identifier for Federal Work

Businesses that plan to bid on federal contracts or apply for federal grants need a Unique Entity Identifier (UEI), a 12-digit number that replaced the old DUNS number Dun & Bradstreet used to issue. The UEI is assigned free through SAM.gov, the federal System for Award Management.¹⁰

Subcontractors or sub-awardees may need only the UEI itself, without a full SAM.gov registration. To apply directly as a prime contractor or grant recipient, a complete registration is required.¹¹ The UEI is unique to an entity at a specific address, so businesses operating from multiple locations may need more than one. Most small businesses never touch the UEI. If federal contracting is even a possibility down the road, registering before an opportunity appears saves you from a process that can take several weeks.

Keeping Your Information Current

Once you have an EIN, you’re responsible for telling the IRS when key details change. File Form 8822-B if your mailing address, physical location, or responsible party changes. Changes to the responsible party must be reported within 60 days.¹²

There’s no direct penalty for not filing the form, but the consequences show up anyway. The IRS may send notices of deficiency or demand letters to your old address or old responsible party, and if you never receive them, penalties and interest keep accruing.¹³

Recovering a Lost EIN

If you’ve misplaced your EIN, check the original notice the IRS sent when you applied, contact the bank where your business account is held, look at previously filed tax returns, or check with state and local agencies where you’ve applied for licenses. If none of that works, call the IRS Business and Specialty Tax Line at 800-829-4933, Monday through Friday, 7 a.m. to 7 p.m. local time. The IRS will verify your identity and provide the number over the phone to authorized individuals.²

1
Internal Revenue Service. Publication 1635 – Understanding Your EIN
2
Internal Revenue Service. Employer Identification Number
3
Internal Revenue Service. Single Member Limited Liability Companies
4
U.S. Small Business Administration. Open a Business Bank Account
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Internal Revenue Service. Topic No. 857, Individual Taxpayer Identification Number (ITIN)
6
Internal Revenue Service. When to Get a New EIN
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Internal Revenue Service. Instructions for Form SS-4 – Application for Employer Identification Number
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Federal Trade Commission. FTC Warns Operators of Websites That Charge for an Employer Identification Number
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Internal Revenue Service. Topic No. 759, Form 940, Employers Annual Federal Unemployment Tax Act (FUTA) Tax Return
10
Export-Import Bank of the United States. SAM.gov and Unique Entity Identifier (UEI)
11
SAM.gov. Entity Registration
12
Internal Revenue Service. About Form 8822-B, Change of Address or Responsible Party – Business
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Internal Revenue Service. Form 8822-B, Change of Address or Responsible Party – Business