If you have started exploring what it takes to run a legitimate US company, you have probably come across the acronym EIN. It shows up in bank account applications, IRS filings, and just about any official document related to your business. But what exactly is it — and why does it matter so much?
What Is an EIN?
EIN stands for Employer Identification Number. It is a nine-digit number issued by the Internal Revenue Service (IRS) that functions as your business's federal tax identification number. Think of it like a Social Security Number, but for your company rather than for you as an individual.
Despite what the name suggests, you do not need to have employees to get an EIN. The name is a relic from when this identifier was primarily associated with payroll. Today, it is required for a wide range of business activities that have nothing to do with employment.
Who Needs an EIN?
Most LLCs and corporations operating in the United States need an EIN. Specifically, you will need one if you plan to:
- Open a business bank account in the US
- File federal tax returns for your company
- Hire employees or contractors
- Apply for business licenses or permits
- Build business credit or take out a business loan
For international founders — those who own a US LLC but live outside the country — the EIN is equally required. Without it, you cannot open a bank account, and without a bank account, conducting business in the US becomes extremely difficult.
How Does It Differ from a Social Security Number?
A Social Security Number (SSN) is assigned to individuals and used for personal tax purposes. An EIN belongs to the business entity itself. When your company files taxes, applies for credit, or opens accounts, it uses its EIN — not your personal SSN. This separation is one of the key benefits of forming a proper legal entity.
How Do You Apply for an EIN?
Online (fastest, but limited): The IRS online application is available Monday through Friday during business hours (Eastern Time). It is only accessible to applicants who have a US Social Security Number or ITIN. If you are a foreign founder without either, this option is not available.
By fax: The most practical option for international founders. Complete IRS Form SS-4, attach your LLC formation documents, and fax everything to the appropriate IRS office. Processing typically takes two to four weeks, though it can stretch to 60–90 days during peak tax season.
By mail: Similar to fax but slower — expect four to six weeks or more outside tax season.
What Is Form SS-4?
Form SS-4 is the official IRS application for an EIN. It collects basic information about your business: the legal name of the entity, its type (LLC, corporation, etc.), the state where it was formed, the reason for applying, and the name and details of the responsible party. Errors or mismatches between your SS-4 and your formation documents are one of the most common reasons the IRS rejects or delays applications.
What Happens After You Apply?
For fax or mail submissions, the IRS will send back a document called a CP575 or a 147c letter confirming your EIN. This is your official proof of tax registration — keep it safe, as you will need to present it when opening bank accounts and in various other contexts.
A Note on Timing
If you plan to launch your business by a specific date, factor the EIN processing time into your schedule. The IRS does not offer guaranteed processing windows, and during tax season delays can be significant. We generally advise founders to apply for their EIN as soon as they have their formation documents in hand, even if they are not yet ready to open a bank account. Getting the application in early gives you a buffer.
At Bridgelyx, we help founders navigate the EIN process as part of a broader formation package. If you have questions about how to complete Form SS-4 or what to do if your application hits a snag, our team is here to help.
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