School Attendance Codes Explained, From I to U
Only four codes count as unauthorised absence. What each code means, which ones are taken out...

No, not usually. The Department for Education’s statutory guidance says schools are not expected to routinely request medical evidence for illness absence and should not have blanket rules requiring it. In most cases your word that your child is too ill for school should be accepted without question. A school can ask for reasonable evidence where it has genuine and reasonable doubt, or where it is trying to support a long or repeated pattern of illness, but even then it should not be fussy about what form that evidence takes.
Every autumn the same message goes round the school gate and the group chats: the office wants a doctor’s note. Parents ring a GP surgery, sit on hold, and are told the practice does not issue notes for schoolchildren, or that it will cost twenty pounds. Then they go back to school empty handed and the absence gets marked unauthorised.
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The July 2026 edition of Working together to improve school attendance is statutory guidance. Schools, academy trusts, governing bodies and local authorities must have regard to it. On illness absence, at paragraph 374, it says:
“Schools are not expected to routinely request that parents provide medical evidence to support illness absences, and should not have blanket rules requiring this. In the majority of cases a parent’s notification that their child is too ill to attend school can be accepted without question or concern.”
That is the starting position. A blanket policy of we need a note for every absence is not consistent with it.
The same paragraph sets out two situations where a school may reasonably ask:
Those are narrower than a standing rule, and the second one is framed as support rather than suspicion. If a school is asking because it wants to help a child who is off a lot, that is a different conversation from a school asking because it does not believe you.
This is the part that saves everyone the most trouble. Paragraph 375 says schools:
“should not be rigid about the form of evidence requested, and should be mindful that requesting additional medical evidence from health professionals can unnecessarily place pressure on health professionals, their staff and their appointment system, particularly if the illness is one that does not routinely require treatment by a health professional.”
The guidance says the starting point should be a conversation with the parent, which may on its own be enough to settle the code. It then names the sort of wider evidence schools may talk to families about: prescriptions, medication and evidence of appointments, and, where a child has an ongoing condition being clinically managed, letters from medical professionals.
And then the single most useful sentence in the document for a parent:
“Where a parent cannot provide evidence in the form requested but can provide other evidence, schools should take this into account.”
So in practice, reasonable evidence is usually something you already have. An appointment card or text confirmation. A prescription or a pharmacy label. A photo of a rash. A record of contact with 111. A clear written account of what happened and when. None of that needs a GP appointment.
GPs are under no obligation to write letters confirming a child was unwell, and many practices charge for them because it is private work that sits outside NHS funding. It is worth saying that to the school plainly, because school offices do not always know it.
Code I, the illness code, covers absence due to illness “both physical and mental health related”. A child who cannot get through the door because of anxiety is not automatically an unauthorised absence.
The guidance is careful here and it is worth being straight about both halves of it. It says that many children experience normal but difficult feelings about school, that those pupils are still expected to attend, and that being away can sometimes make it harder to go back. It also says that some pupils face more complex barriers, including those with long term physical or mental health conditions or with special educational needs and disabilities, and that for those pupils:
“Their right to an education is the same as any other pupil and therefore the attendance ambition for these pupils should be the same as it is for any other pupil but additional support may need to be provided.”
Where a child is disabled within the meaning of the Equality Act 2010, the guidance points schools at formal reasonable adjustments under section 20 of that Act, agreed with and regularly reviewed with the pupil and parents. That is a legal duty, not a favour.
Nothing here needs a fight. In order:
If your child has been out of school for a long stretch, or looks likely to be, read the section 19 duty. Your council has a legal responsibility to arrange suitable education for a child who cannot attend because of illness, and almost nobody is told about it.
Whether an absence is authorised or unauthorised is a coding decision, and the codes are set out in law. Illness is code I and counts as authorised. An absence with no established reason becomes code O and counts as unauthorised. Arriving after the register closes is code U, which is also unauthorised even though your child is in school that day.
Those distinctions matter, because unauthorised sessions are what count towards a fine. Our guide to the attendance codes goes through the ones parents actually meet, and the rules on attendance fines explains the threshold.
In 2024/25, 176,361 children in England missed at least half of school, and severe absence has kept rising even as overall absence improved. Illness is the single largest reason for absence nationally. See the absence figures for your council.
Not as a matter of routine. The statutory guidance says schools are not expected to routinely request medical evidence for illness absence and should not have blanket rules requiring it. In most cases a parent’s notification that a child is too ill for school can be accepted without question.
A school decides which code to record, so in principle it can decline to treat an absence as illness if it is not satisfied. But it is expected to have a conversation first, to accept reasonable evidence rather than insisting on one particular form, and not to apply a blanket rule. If it doubts the illness, ask it to tell you that directly and say why.
Often not. Writing a letter to confirm a child was unwell is private work outside NHS funding, so practices are not obliged to do it and many charge a fee. The guidance recognises this and asks schools to be mindful of the pressure that requests place on health professionals.
The guidance deliberately does not set a list, and tells schools not to be rigid about the form. In practice, appointment cards or texts, prescriptions and pharmacy labels, records of contact with 111, photographs of a visible symptom, or a clear written account of what happened can all be reasonable.
Yes. The illness code covers absence related to both physical and mental health. Where a child is disabled within the meaning of the Equality Act 2010, the guidance also points schools towards formal reasonable adjustments under section 20 of that Act.
Fines follow unauthorised absence. Illness recorded as code I is authorised and does not count towards the threshold for a penalty notice. The risk comes when absences are recorded as unauthorised instead, which is why it is worth checking how sessions have actually been coded.
This is information, not legal advice
Darling Mellow is a parenting website. We are not solicitors, we are not regulated to give legal advice, and nothing here is advice about your particular child or situation. We write about the law in England, we date everything and we link our sources so you can check them. Deadlines and duties change, and only you know your full circumstances, so please take proper advice before making a decision that matters.
Where to get free or regulated advice
If you are in Wales, Scotland or Northern Ireland, the law and the services differ and you should use your own nation’s guidance.
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