Editing Unique Master Citizen Number (section)

===Checksum calculation===

The checksum is calculated from the mapping {{not a typo|DDMMYYYRRBBBK}} = ''{{not a typo|abcdefghijklm}}'', using the formula:
:''m'' = 11 &minus; (( 7×(''a'' + ''g'') + 6×(''b'' + ''h'') + 5×(''c'' + ''i'') + 4×(''d'' + ''j'') + 3×(''e'' + ''k'') + 2×(''f'' + ''l'') ) [[Modulo operation|mod]] 11)

* If ''m'' is between 1 and 9, the number K is the same as the number ''m''
* If ''m'' is 10 or 11 K becomes 0 (zero)

Note: there has been a small number of JMBGs that were assigned by valid authorities but which had an invalid checksum. Also, there are a few duplicate JMBGs in existence. The common anecdotal explanation for these is simple operator error. Reportedly these mistakes happened more often in the early 1990s. The chances of running into exceptions are reportedly low, and whether such exceptions justify questioning the use of JMBG as a unique identifier has not been scientifically analyzed.{{Citation needed|date=December 2010}}