Tax Identification Number - TIN

A Tax Identification Number (TIN) is a nine-digit number used as a tracking number by the U.S. Internal Revenue Service (IRS) and is required information on all tax returns filed with the IRS. Employer tax ID numbers are issued to businesses by the IRS. These numbers are also nine digits long, but they are read as XX-XXXXXXX. 

Tax Identification Numbers come in several different forms. Individuals are assigned TINs in the form of Social Security Numbers (SSNs), whereas businesses such as corporations and partnerships are assigned employer identification numbers (EINs). SSNs are tax identification numbers for individuals, and the Social Security Administration (SSA) issues them in the format of XXX-XX-XXXX. Trusts, fiduciaries and other non-business entities are assigned straight tax ID numbers. Other types of TINs include the Individual Taxpayer Identification Number (ITIN), the Adoption Taxpayer Identification Number (ATIN) and the Preparer Tax Identification Number (PTIN).

The IRS uses tax identification numbers to track taxpayers. The IRS issues all tax identification numbers except for SSNs. Filers must include the number on tax-related documents and when claiming benefits.

The tax identification number is also known as the taxpayer identification number. 

The SSN is the most common form of tax identification numbers. A child must have a SSN before a parent can claim that child as a dependent for income tax purposes, so most parents voluntarily apply for the number on behalf of their children. The SSA processes applications for free, but there are also fee-based services that offer to complete applications for new parents.

The IRS uses the Employee Identification Number (EIN) to identify corporations, trusts and estates that must pay taxes. These groups must apply for the number and use it to report their income for taxation purposes. Applying for an EIN is free and a business can obtain one immediately. 

The IRS issues ITINs to certain nonresident aliens who do not otherwise qualify for a SSN. The spouse of a nonresident alien must include the number on his tax returns when he files. In order to get an ITIN, the applicant must complete Form W-7 and submit documents supporting his status as a nonresident alien. Certain agencies — including colleges, banks and accounting firms — are able to help applicants obtain their ITIN. 

The ATIN only applies to domestic adoptions when the adoptive parents cannot obtain the child's SSN in time to complete their tax returns in a timely manner. To qualify, the child must be a U.S. citizen and the adoption must be pending.

The IRS began requiring listing of a PTIN on each return a tax preparer files beginning on Jan. 1, 2011. Prior to this date, use of the PTIN had been optional. Any preparer that charges to complete all or part of the tax return or refund for another individual must have and use the PTIN.