In the first book Hermione mentions that she has tried a few spells, before ever arriving at Hogwarts, Sorcerer's Stone, Ch 6:

I've tried a few spells just for practice and it's all worked for me.

Clearly she didn't get into trouble for that. In the second book after Dobby performs a Hover Charm Harry receives a letter from the Ministry of Magic, in Ch 2:

We have received intelligence that a Hover Charm was used at your place of residence this evening at twelve minutes past nine.

As you know, underage wizards are not permitted to perform spells outside school, and further spellwork on your part may lead to expulsion from said school (Decree for the Reasonable Restriction of Underage Socery, 1875, Paragraph C).

We would also ask you to remember that any magical activity that risks notice by members of the non-magical community (Muggles) is a serious offense under section 13 of the International Confederation of Warlocks' Statute of Secrecy.

In the fifth book (Order of the Phoenix) Ch 2 Harry receives a letter after saving Dudley from the Dementors:

We have received intelligence that you performed the Patronus Charm at twenty- three minutes past nine this evening in a Muggle-inhabited area in the presence of a Muggle.

The severity of this breach of the Decree for the Reasonable Restriction of Underage Sorcery has resulted in your expulsion from Hogwarts School of Witchcraft and Wizardry. Ministry representatives will be calling at your place of residence shortly to destroy your wand.

As you have already received an official warning for a previous offense under section 13 of the International Confederation of Wizards' Statute of Secrecy, we regret to inform you that your presence is required at a disciplinary hearing at the Ministry of Magic at 9 A.M. on August 12th.

Students appear to use magic outside of Hogwarts, without getting in trouble, except for Harry Potter. In the movies the violations are even worse, with Hermione repairing Harry's glasses, Harry casting Lumos Maxima repeatedly in his bedroom.

What is the level of severity (or complexity) of spell which will generate the notice of the Ministry of Magic?

  • 1
    It's also possible Dumbledore has something to do with this, since he might want a tighter trace on Harry than on others so he can keep up with what's going on or get some kind of notice if something happened to him.
    – Tango
    Nov 30, 2011 at 6:00
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    If I remember, Once students board the Hogwarts Express, they are technically on Hogwarts property and can cast spells. Nov 30, 2011 at 6:00
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    Moving over to the movies, it's also noteworthy that Harry Potter doesn't get any notices for using his wand as a flashlight under the covers when he's studying.
    – Iszi
    Nov 30, 2011 at 14:26
  • @Iszi - They probably appreciated a good metaphor as much as the rest of us.
    – Valorum
    Dec 5, 2018 at 21:47
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    @T.Sar-ReinstateMonica Which holes? It's clear MoM can only detect remote magic, not who performed it. With wizarding families, they rely on parents to enforce the rule. Harry only gets blamed because he is the only wizard around. Also, the punishment is not serious until the MoM was trying to discredit Harry. Dec 7, 2019 at 16:04

6 Answers 6


In the FAQ on her website, J.K. Rowling says:

Q: In "Philosopher's Stone" Aunt Petunia says that Lily came back from Hogwarts with frog spawn in her pockets and turned teacups into rats. If this is true, why wasn't Lily expelled?

A: Aunt Petunia is exaggerating a little; you have to allow for her state of mind when she started shrieking these things. However, just like her son, Lily was not averse to testing the limits of the Statute of Secrecy, so you can safely assume she will have had a few warning letters – nothing too serious, though.

Once on the Hogwarts Express, the students appear to be able to do magic without consequence. For example, Ron's Sunshine, daisies, butter mellow spell on Scabbers (SS, though it was probably not a real spell), Ginny's Bat Bogey hex on Zacharias Smith (HBP), and Draco Malfoy's Petrificus Totatlis on Harry (HBP).

According to J.K. Rowling, it would seem any incident of underage magic would result in a Mafalda Hopkirk (Improper Use of Magic Office) letter, but I'd suggest there are tiered responses depending on the spell cast by the underage wizard. Frog spawn and teacups? A little "tsk-tsk". A hover charm and a smashed pudding? Perhaps a more stern warning. The Patronus Charm? Very advanced magic -- expulsion from Hogwarts.

Frankly, I find canon to be very inconsistent when it comes to underage magic. How could underage Tom Riddle have performed such extensive and dark magic on his Gaunt and Riddle relatives without receiving at least a warning? (The idea of getting a Hopkirk letter for the offense of underage Avada Kedavra is somewhat darkly amusing . . . )

I personally don't consider the movies to be canon, but I've certainly rolled my eyes at the inconsistencies they contain. For what it's worth, the spell Harry casts at the beginning of Prisoner of Azkaban is Lumos Maxima.

  • One might say that if magic can progress, the way technology does, that they eventually got better at detecting underage magic. Although it is still pretty sad that they blamed Dobby's Hover Charm on Harry. Nov 30, 2011 at 16:48
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    Also, it seems likely that underage Tom Riddle learned a spell to conceal his illegal misuse of magic. He was certainly good at defeating search spells later.
    – Tynam
    Nov 30, 2011 at 16:52
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    @JackBNimble - I think they probably got better at it as well. I found it interesting that the concept of "the trace" wasn't really explored until book seven. Nov 30, 2011 at 17:22
  • @Tynam - I don't think Tom Riddle could have done that. In Half-Blood Prince, Dumbledore says, "Magic always leaves traces [...] sometimes very distinctive traces. I taught Tom Riddle. I know his style." (HBP - Pg 563 - US Hardcover). Off the top of my head, the two spells that might qualify as a "search" spell are Homenum Revelio and Accio (obliquely) -- Snape doesn't use a specific spell to force the Marauder's Map to reveal itself. Are there "searching" spells I'm not thinking of? Nov 30, 2011 at 17:33
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    @Slytherincess Sorry, I wasn't necessarily referring to divination as defined in HP, but divination in general. Making the unseen seen. Homenum Revelio, the Trace, and the magic used in creating the Marauder's Map are some examples. I'm kinda going on the assumption that we haven't seen all the spells known in-universe ;)
    – Izkata
    Feb 14, 2012 at 12:59

It seems to me that the decree only affects people who are currently in school, but not at Hogwarts. Students not old enough for school yet don't seem to get into any kind of trouble for using magic.

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    Seems to be supported by accidental usage (and Tom Riddle's purposeful usage as a child before Hogwarts) not getting people in trouble
    – Izkata
    Nov 30, 2011 at 12:50
  • Too, most wizards are probably born into wizarding families and aren't really a risk factor in exposing the wizarding world to Muggles.
    – Xantec
    Nov 30, 2011 at 12:50
  • @Xantec: Started to try to guess the percentage of wizards born to a muggle born family, decided that it would make an interesting question. So, I posted at scifi.stackexchange.com/q/7364/98 to find the answer. Nov 30, 2011 at 14:00
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    @Slytherincess Two half-blood wizards having children would still have half-blood children, but those children would be born into a wizarding family. Carry this on for a few generations with families like the Malfoys and the Blacks keeping it "in the family" so to speak, and the half-bloods would soon out number the pure-bloods even without any new half-blood wizards/witches like Hermione. So Hagrid's statement would still be true even if most magically inclined children are born into a wizarding family.
    – Xantec
    Nov 30, 2011 at 15:42
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    @Xantec Yes, I was agreeing with you in my first comment. I'm sorry if I didn't make that clear! I wanted to just note Hagrid's comment on the matter. But, yes, I believe you're right -- most children would be born into Wizarding families, whether pureblood or half-blood. :) Nov 30, 2011 at 15:53

The ministry does not know that it is an underage wizard or witch doing magic if they are surrounded by other fully qualified witches or wizards; that's why Hermione can do magic on in Diagon Alley and why Fred and George can do magic at their home. As for Hermione saying that she has already tried a few spells at home i think that the ministry was just letting her off because she hadn't actually attended Hogwarts yet.

This is addressed directly by Dumbledore in HBP, page 368:

"But how come the Ministry didn't realize that Voldemort had done all that to Morfin?" Harry asked angrily. "He was underage at the time, wasn't he? I thought they could detect underage magic!"

"You are quite right -- they can detect magic, but not the perpetrator: You will remember that you were blamed by the Ministry for the Hover Charm that was, in fact, cast by --"

"Dobby," growled Harry; this injustice still rankled. "So if you're underage and you do magic inside an adult witch or wizard's house, the Ministry won't know?"

"They will certainly be unable to tell who performed the magic," said Dumbledore, smiling slightly at the look of great indignation on Harry's face. "They rely on witch and wizard parents to enforce their offspring's obedience while within their walls."

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    And in DH, the Trace is introduced, which screws this up.
    – user35971
    Dec 17, 2014 at 4:12
  • @user35971 You're mixing up the Trace with the Taboo. The Trace detects underage magic (but can't tell who performed it), the Taboo detects the usage of the word "Voldemort".
    – IloneSP
    Jan 8, 2020 at 12:08

Before they're old enough to have a wand, they usually can't control it, and without a wand it's much weaker, usually not strong enough to do harm. Tom Riddle could control his magic and do some harm with it, but he didn't know he was a wizard so they couldn't really punish him for it. I just glanced over the conversation in book six, and Dumbledore didn't even tell him not to use magic until he got to Hogwarts. It must not start until they get there.

On the Hogwarts express, I'd think it's ok, as it's only students, with the occasional teacher (Lupin). It'd be hard to enforce there anyway... An i just thought of the fact that they can't tell who cast the spell, so on the HE, it would register on a dozen traces.

Harry's Dobby experience seems to be a fairly standard procedure, and I'm sure he could have gotten that cleared up eventually, though probably not until he freed Dobby.

The Aunt Marge fiasco was overlooked by the ministry, probably on orders from Cornelius Fudge himself, because they wanted to keep Harry safe from Sirius. Harry actually discusses this with the Minister (p.45, PoA, first American Ed.). It's nearly a page so I won't post it, but it boils down to being overlooked so they could keep him safe.

In OotP, remember, the Ministry is looking for any excuse to discredit him (because they don't want to face the fact that Voldemort is back), and Dumbledore has to "remind" them that there is an exception in cases of saving a life. Even so, they try to disprove, discredit, and completely overlook that exception, because they're trying to discredit him. It's sort of the opposite of the book 3 response.

As for Lumos in the movies, I'd say that is more for screen effect, and I wouldn't take it as canon.


It seems to me that the Trace is placed and activated upon the young wizards and witches when they start school.

As you know, underage wizards are not permitted to perform spells outside school.

Let me propose that "school" is not referring to the geographical, but to the temporary location. It ist not monitoring on the Hogwarts Express, because school term begins when they board it (i.e. September 1st). For example, when Ron tries his magic on Scabbers on the first book. The same applies for the weekends at Hogsmead. Therefore, there is no point arguing why the Trace didn´t monitor Harry's spells while in the Triwizard Tournament (or in the cemetery with Voldemort).

It monitors between terms (summer vacations) and only when there are not qualified wizards near the underage wizard when magic is performed. That´s why Fred and George are able to experiment at home: they live in a household with qualified wizards. The parents have then the responsibility of monitoring their children.

They rely on witch and wizard parents to enforce their offspring's obedience while within their walls.

Harry Potter didn´t live with qualified wizards. Dobby didn´t qualify as such, and when he performed the hover charm, Harry was warned. Compare it with the occasion when Tonks did magic (packing and cleaning) at his home. The spellwork would be attributed to her. Other examples would demonstrate this point: when Mr. Weasley undid the engorging charm on Dudley; or when Dumbledore came to pick up Harry and did his bits of magic.

The Patronus charm (Order of the Phoenix) was casted when no other wizard was present, thus charging again Harry for it. This time the spellwork was not only complex, but it also breached the Statute of Secrecy. Such major offense would have granted him the expulsion from school.

It was very different when Harry accidentally "blew up" his Aunt Marge. He didn´t use a spell, he didn´t use his wand. It was uncontrolled magic. Thus, he didn´t receive a letter from Mrs. Hopkirk while he was packing his trunk to run away from home.


I always took the Lumos Maxima usage by Harry in the film adaption of Azkaban just emphasized that the Ministry was being especially lenient on him due to Blacks escape.

I would also say that once students are on the Hogwarts Express magic is allowed from that point on.

And as for Tom Riddle casting killing curses on his victims whilst at Hogwarts- perhaps the Ministry weren't quite as strict and didn't monitor students in the 1940's?

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