The first SSN was issued in 1936. These numbers are only given to U.S. Citizens and permanent residents. The ITIN, introduced in 1996, was established so that taxpayers who do not qualify for a SSN can still file taxes.
Both the ITIN and SSN contain nine numbers, and they both function as tax identification numbers.
The ITIN is issued by the Internal Revenue Service, whereas the SSN is issued by the Social Security Administration. The ITIN is not a valid form of identification, and can only be used for tax purposes. The SSN, although it was never its intended use, is now considered a valid form of identification for many purposes. The Social Security Administration provides taxpayers with a Social Security Card. The Internal Revenue Service discontinued issuing cards imprinted with ITINs to avoid any resemblance to the Social Security Card, and now issues a letter instead.
The method of ascertaining whether a number is an ITIN or a SSN is quite simple. The ITIN always begins with the number nine and the fourth and fifth digits are always a seven or an eight.
Not everyone is required to have a SSN or ITIN, although they are required by parents for claiming their children as dependents on their federal income tax returns.