National Insurance number
The National Insurance number is used as a reference number in the Pay As You Earn system, and also by the self-employed. It is also used in applications for Individual Savings Accounts (ISAs), to check that an individual has opened only one ISA in a tax year.
Social Security (United States)
Obtaining a Social Security number for a child is voluntary. Further, there is no general legal requirement that individuals join the Social Security program unless they want or have to work. Under normal circumstances, FICA taxes or SECA taxes will be collected on all wages. About the only way to avoid paying either FICA or SECA taxes is to join a religion that does not believe in insurance, such as the Amish, Christian Science or a religion whose members have taken a vow of poverty (see IRS publication 517 and 4361). Federal workers employed before 1987, various state and local workers including those in some school districts who had their own retirement and disability programs were given the one-time option of joining Social Security. Many employees and retirement and disability systems opted to keep out of the Social Security system because of the cost and the limited benefits. It was often much cheaper to obtain much higher retirement and disability benefits by staying in their original retirement and disability plans. Now only a few of these plans allow new hires to join their existing plans without also joining Social Security. In 2004, the Social Security Administration estimated that 96% of all U.S. workers were covered by the system with the remaining 4% mostly a minority of government employees enrolled in public employee pensions and not subject to Social Security taxes due to historical exemptions.