A Taxpayer Identification Number (TIN) is a number that the Internal Revenue Service uses to manage and enforce tax laws. You will need a TIN to use on tax returns and statements as well as other tax documents.
Complete a Form SS-5 from the Social Security Administration to get a Social Security card if you are a U.S. citizen (see Resources below). You will need this number for your individual tax returns.
Obtain an EIN for any business located in the U.S. or its territories. Generally, businesses need EINs to identify themselves on tax documents. Also, if your business structure changes, you probably will need a new EIN.
Apply for an EIN. The IRS prefers you apply for an EIN using the online application form (see Resources below). However, you can also apply by phone toll free at (800) 829-4933 or by fax or mail using IRS Form SS4 (see Resources below).
Get an Individual Taxpayer Identification Number if you are a certain type of resident, a nonresident alien, or a spouse or dependent of a nonresident alien and cannot get a Social Security number. To do this, complete IRS Form W7, Application for Individual Taxpayer Identification Number (see Resources below).
Inquire about an Adoption Taxpayer Identification number if you are adopting a U.S. citizen or resident child and you can't get a SSN before it is time to file your tax return. This is a temporary nine-digit number.
Provide evidence of your age, identity, and status as a U.S. citizen or legal alien when you apply for a Social Security number.