School absence codes explained: Code I, Code O, C2 and more
The code a school uses for each missed session matters. It decides whether an absence is authorised and whether fines are possible.
The codes parents most need to know
Code I – Illness (not medical appointments). Authorised. This is the right code when your child is too unwell to attend, including because of mental health.
Code M – Medical or dental appointment. Authorised.
Code C2 – Authorised absence on an agreed part-time (reduced) timetable. Introduced in 2024, so sessions your child isn't expected in don't count against them.
Code O – Unauthorised absence not covered by another code. This is the code that can lead to penalty notices.
How to check your child's codes
You can ask the school for your child's attendance record at any time. Ask for the codes, not just the percentage.
If illness has been coded as O, write and ask for it to be corrected, giving the dates and reasons.
Medical evidence
DfE guidance says schools should not usually need medical evidence to authorise illness. In a minority of cases they may ask, and a GP appointment card or prescription is often enough. You can't be required to get a GP note for every day.
Questions parents ask
What absence code should schools use for mental health?
Code I (Illness). The DfE's guidance confirms mental health illness is covered.
What is Code C2?
C2 is for sessions a child isn't expected to attend because they are on a temporary, agreed part-time timetable.
More guides
General information for families in England, not legal or medical advice. Checked against DfE guidance current in 2026.