What is a valid UPN?
In order to be valid a UPN must: (a) be 13 characters long; (b) have a recognised LA(or pseudo-LA, e.g. the Service Children’s Education Authority) code for characters 2-4; (c) have digits for characters 5-12; (d) have a digit or an upper case letter other than I, O or S for character 13; (e) have the correct upper case ‘check letter’ at character 1 derived by a specified formula from characters 2-13, as detailed in question 12.
