Every absence is recorded in the attendance register with a national code, and each code is classed for statistics as attending, authorised absence, unauthorised absence or not a possible attendance (attendance guidance, chapter 8). Authorised absence covers things like illness (code I), medical appointments (M) and leave of absence the school has granted. The school, not the parent, decides which code applies.
The four unauthorised codes are:
- G: holiday the school hasn't granted. Leave can't be granted after the event (paragraphs 404 and 405).
- N: reason not yet established. It must be replaced with the correct code within 5 school days, or changed to O (paragraphs 407 and 408).
- O: absent in other or unknown circumstances, or the school isn't satisfied with the reason (paragraph 410).
- U: arrived after the register closed. The register may be open for no more than 30 minutes (paragraphs 412 and 413).
Unauthorised absence matters for safeguarding as well as attendance. Schools should contact parents on the first day of an unexplained absence, and tell a pupil's social worker about unexplained absences (paragraphs 42 and 52). KCSIE 2026 paragraph 221 says absence can be a warning sign of neglect and exploitation.
It also triggers formal steps. Ten sessions of unauthorised absence within a rolling 10 school weeks means the school or local authority must consider a penalty notice (paragraph 184).