National Insurance number
The National Insurance number is a number used in the United Kingdom in the administration of the National Insurance or social security system. It is also used for some purposes in the UK tax system. The number is described by the United Kingdom government as a "personal account number".
Social Security (United States)
Although Social Security is sometimes compared to private pensions, the two systems are different in a number of respects. It has been argued that Social Security is an insurance plan as opposed to a retirement plan. Unlike a pension, for example, Social Security pays disability benefits. A private pension fund accumulates the money paid into it, eventually using those reserves to pay pensions to the workers who contributed to the fund; and a private system is not universal. Social Security cannot "prefund" by investing in marketable assets such as equities, because federal law prohibits it from investing in assets other than those backed by the U.S. government. As a result, its investments to date have been limited to special non-negotiable securities issued by the U.S. Treasury, although some argue that debt issued by the Federal National Mortgage Association and other quasi-governmental organizations could meet legal standards. Social Security cannot by law invest in private equities, although some other countries (such as Canada) and some states permit their pension funds to invest in private equities. As a universal system, Social Security generally operates as a pipeline, through which current tax receipts from workers are used to pay current benefits to retirees, survivors, and the disabled. When there is an excess of taxes withheld over benefits paid, by law this excess is invested in Treasury securities (not in private equities) as described above.