Generally, an employer is a person or organization for whom a worker performs services as an employee. As an employer, you are generally required to withhold, report, and pay employment taxes. To file the various tax returns, including employment tax returns, you need a Taxpayer Identification Number (TIN). The TIN for organizations is an Employer Identification Number (EIN). However, a sole proprietor may use his or her social security number as the TIN if the business has no employees and is not required to file excise, employment, alcohol, tobacco, or firearms returns. A sole proprietorship is the only type of business that may use a social security number as its TIN.

An entity is considered to be a sole proprietorship for Federal tax purposes if an individual operates his or her business through a domestic Limited Liability Company (LLC) owned solely by the individual and does not elect for that LLC to be taxed as a corporation using Form 8832 (PDF), Entity Classification Election. In such a case, the LLC is disregarded for Federal tax purposes. Generally, the disregarded LLC should not request its own EIN. However, the owner of a disregarded LLC may choose to have the disregarded LLC pay all employment taxes and file employment tax returns with respect to wages paid to employees performing services for the disregarded LLC using the disregarded LLC's own name and EIN.

There are four ways to apply for an EIN:

1. The Internet EIN (I-EIN) application is the most convenient method for customers to apply for and obtain an EIN. Once all the necessary fields are completed on the online form, preliminary validation is performed and the taxpayer will be alerted to information IRS needs that may not have been included. A provisional EIN will be issued after the successful submission of the completed Form SS-4 online. While this EIN can be used to open a bank account, apply for a business license, make a tax payment, or file a paper tax return, it will not be available for use on any IRS electronic system (such as e-File or TIN matching) for approximately 7–10 days. Please note that not all business entity types may use this method.
2. You may obtain an EIN immediately by telephone 5 days a week, Monday through Friday from 7:00 a.m. to 10:00 p.m. (local time), by calling IRS at (800) 829–4933.
3. You may obtain an EIN by completing Form SS-4 (PDF), Application For Employer Identification Number, and faxing it to the IRS for processing. The IRS Fax numbers are provided in the Form SS-4 Instructions. An EIN applied for by fax will be issued within 4 business days.
4. You may also obtain an EIN by completing the Form SS-4 and mailing it to the IRS service center address listed on the Form SS-4 Instructions. By mailing the completed Form SS-4 to the appropriate service center, you can obtain an EIN within 4 to 6 weeks.

If you already have an EIN and the organization or ownership of your business changes, you may need to apply for a new number. Some of the circumstances under which a new number is required are as follows:

1. You incorporate
2. An existing business is purchased or inherited by an individual who will operate it as a sole proprietorship, unless the new owner already has an EIN
3. The sole proprietorship becomes a partnership
4. A partnership changes to a sole proprietorship
5. A corporation changes to a partnership or a sole proprietorship
6. You file bankruptcy under Chapter 7; or
7. An individual owner dies, and the estate takes over the business

Note: This list is not all-inclusive.

For more information, refer to Publication 1635 (PDF), Understanding Your EIN. If you prefer, you may call 1–800–829–4933 for more information.