A federal tax identification number is also known as the Employer Identification Number (EIN). All the employers need to have it in order to be tracked by the government regarding the tax payments and tax return filings. The EIN is a long nine-digit number and helps the Internal Revenue Service (IRS) to keep a check on your tax-related activities. Therefore, all employers are expected to have it, in the same way the employees should have the social security number (SSN). For individuals who are handling a proprietorship without any employees, having an SSN would be just as fine, for most parts. How to Apply If you already have been issued an EIN, and are planning to start a new business, you needn't apply for this number again, the previous one would work just as fine. In a situation wherein you have ended up misplacing this number, you will have to visit the official website of Internal Revenue Service (IRS.gov) and follow the written instructions. You can try to find the confirmation notification sent by the IRS on your email. Also, if you have used your EIN for opening a bank account, then you can try getting the details from the bank. If you still fail to find information related to your previous EIN, then you can find helpline numbers on the official website of IRS. In case you are applying for this number for the very first time, you need to follow the procedure mentioned below. Internet Application This is one of the most fastest, as well as the most preferred method of application. You need to fill up an online application, wherein the information is validated and checked during an online session. As soon as you have entered all the information correctly, an EIN is issued immediately. This option is available for the citizens of the United States only. Application via Telephone You can also apply through a toll-free telephone service initiated by the IRS. The details of the numbers and operating hours are available at the official website of IRS. Application by Fax Fill out Form SS-4 and send it to the fax number given for your state. Make sure that your fax number is mentioned in the application and that all the necessary information on Form SS-4 is filled correctly. Once your fax is received by the authorities and the required procedure is done, they will send you a fax with an EIN, within four business days, provided your application has all the required information. Application by Mail The procedure is the same as applying through fax, just that instead of fax, you are sending the application along with the correctly filled Form SS-4, through mail. This method takes a little more time as compared to others. The entire process takes at least 4 weeks. You will be reverted back through mail with the EIN. Check the IRS website for details. Keep in mind that it takes about 2 weeks for the EIN to be a part of the permanent records held by the IRS. Therefore, it is advisable to wait for two weeks to use your IRS-related identification numbers for filing returns or paying taxes.