<P> In 1993, a one - off mass allocation of NI numbers was made to all children under the age of 16 whose parents were in receipt of Child Benefit . As a result of this, siblings who met the criteria above were allocated NI numbers sequentially . </P> <P> Persons from abroad who wish to work in the UK, or those to whom a number was not initially allocated as children, must apply for a number through the Department for Work and Pensions (DWP). The prefixes used are typically different from those used in the normal run . </P> <P> The format of the number is two prefix letters, six digits, and one suffix letter . The example used is typically QQ123456C . Often, the number is printed with spaces to pair off the digits, like this: QQ 12 34 56 C . </P> <P> Neither of the first two letters can be D, F, I, Q, U or V . The second letter also cannot be O . The prefixes BG, GB, NK, KN, TN, NT and ZZ are not allocated . Validation lists of issued two - letter prefixes are published from time to time . </P>

How many digits is a uk national insurance number