What Is IRS Form SS-4?

Form SS-4 is the IRS application for an Employer Identification Number, or EIN. An EIN is like a Social Security number for a business — it's a nine-digit tax ID number the IRS uses to track a business entity's tax obligations. Most businesses need one, and getting an EIN is free.

Who Needs an EIN

You need an EIN if you have employees, operate as a corporation or partnership, have a Keogh plan, file certain tax returns (estate, trust, alcohol/tobacco), withhold taxes on non-wage income paid to non-resident aliens, or are involved with certain types of organizations. Many sole proprietors with no employees get an EIN too, even though it's not strictly required, to avoid giving out their Social Security number to clients.

How to Apply

The easiest way to get an EIN is online through the IRS website at irs.gov. The online application is available for entities whose principal business is located in the U.S. or U.S. territories. You can complete the application in about 15 minutes and receive your EIN immediately. You can also apply by fax or mail using Form SS-4, though those methods take longer.

What You'll Need

To complete Form SS-4, you need to provide the legal name of the business, the type of entity (sole proprietor, LLC, corporation, partnership, etc.), the reason you're applying for an EIN, the principal location of the business, and the name and SSN or ITIN of the responsible party — the individual who owns or controls the entity.

LLCs and EINs

A single-member LLC that doesn't have employees and hasn't elected to be taxed as a corporation doesn't technically need an EIN — it's a disregarded entity and uses the owner's SSN for tax purposes. But many single-member LLC owners get an EIN anyway for privacy and professionalism, and any LLC with employees or multiple members needs one.