This error occurs if you have pupils aged 14 and above on Census Day who are missing a unique learner number (ULN)
Unique Learner Number must be present for pupils aged 14 and over on census day, that is, for autumn census with a date of birth of 06-10-2008 or earlier; spring census with date of birth of 19-01-2009 or earlier and for summer census with date of birth of 18-05-2009 or earlier.
On the student profile's Extended Tab, the ULN is entered in the School Information section.