National Identity Number: NIMC insists on identification for enrolment

The National Identification Number (NIN) is a set of numbersassigned
to an individual upon successful enrolment. Enrolment consists of the
recording of an individual's demographic data and capture of the ten
(10) fingerprints, head-to-shoulder facial picture and digital
signature, which are all used to cross-check existing data in the
National Identity Database to confirm that there is no previous entry
of the same data. Once this (de-duplication) process is completed the
data is then stored with a unique NIN that was assigned to it.

The NIN once issued to a person cannot be used again, (that is, it
cannot be issued to another person even if the previous person is
dead). It is the NIN that helps to tie all records about a person in
the database and is used to check the identity verified.
Source:Vanguard