The short answers
What is unauthorised absence?
Absence the school has not accepted. It is recorded with one of four codes: G, a holiday the school did not grant; N, a reason not yet established; O, absence in other or unknown circumstances; and U, arriving after the register closed.
What is authorised absence?
Absence the school has given permission for, or that the law accepts, such as illness (I), a medical or dental appointment (M), religious observance (R), exceptional circumstances the headteacher has agreed (C), or leave for an interview (J1). It still counts as absence in the pupil's attendance.
Does authorised absence count against attendance?
Yes. Authorised and unauthorised absence both reduce a pupil's attendance and both count towards persistent absence, which is missing 10% or more of possible sessions. Only unauthorised absence counts towards the penalty notice threshold.
How many unauthorised absences before a fine?
The national threshold for a school to consider a penalty notice is 10 sessions of unauthorised absence in a rolling period of 10 school weeks, in any combination, such as term-time holiday and late arrivals after the register closes. A school has to consider each case on its merits, and the first question the DfE asks it to consider is whether support is appropriate. Knowing which families are getting close is how a fine is avoided.
Keeping the codes right
Most unauthorised absence that should not be there is a code that was never updated.
Resolve N codes quickly
N means the reason is not yet known. It must be replaced with the right code as soon as the reason is known and no more than five school days after the session, or changed to O if no reason can be found.
Check late marks against the register close
L, before the register closed, is present. U, after it closed, is unauthorised absence for the session and counts towards the threshold.
Watch the running count, not the term
The ten school weeks roll and can cross terms and school years, so a count taken at the end of a term misses families who are already close.
Where this comes from
- Working together to improve school attendanceThe DfE's statutory guidance, 2026 edition: what schools, trusts and local authorities are expected to do.
Related guides: every attendance code, the ten-week duty, persistent and severe absence. Every guide is listed on the guides page.
The count, kept for you
adsum reads the codes in the exports your MIS already produces, lists the N codes still waiting for a reason, and counts unauthorised sessions over the exact ten school weeks for every pupil, so a family can be supported long before a fine is discussed.
Or ask us for a trial on your own school's data.