<P> National Insurance numbers issued in the Isle of Man hold the prefix MA . Similarly, those issued in Jersey start with JY, and those issued in Guernsey hold the prefix GY . Only Channel Island NINOs issued prior to 1975 are validated, and recognised for UK use by HMRC . </P> <P> 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 . </P> <P> However, the NI number is not used universally as a tax identification number . Taxpayers who need to file a tax return are given a different number, a Unique Taxpayer Reference (UTR), which is used as a reference number in the self - assessment tax system . </P> <P> NI numbers are sometimes used for identification purposes in other contexts which have nothing to do with their original National Insurance purpose--such as forming part of evidence of right to work in the UK . The NI card, however, is not proof of identity . </P>

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