The inciting incident is the event that disrupts a character's ordinary life and makes the rest of the story necessary. Before it, the character could have gone on as they were. After it, they cannot — and everything that follows is a response.
The test is one question: if this had not happened, would there still be a book? If yes, it is not your inciting incident.
Three things it is not
It is not the opening. The opening is the first page; the inciting incident is usually a little later, once we know enough about the ordinary life to feel it break. A story can open in the middle of chaos and still have its inciting incident further in — that is the structure described in in medias res.
It is not the hook. The hook is a craft device for holding attention: a striking line, an unanswered question. The inciting incident is a structural event. A strong hook with no incident is the commonest shape of a draft that stalls at chapter four. More on the first of those jobs in opening lines that lose readers.
It is not the first thing that goes wrong. Plenty of trouble is just texture. The inciting incident is the trouble that cannot be absorbed — the one the character has no existing routine for.
What makes one work
It is irreversible. If the character could put things back and go home, nothing has started. A letter can be unanswered; an eviction cannot.
It forces a choice rather than a reaction. The strongest version does not simply happen to someone; it puts them in a position where doing nothing is also a decision with a cost.
It is specific to this character. The same event should mean something different to them than it would to anybody else. A job offer is nothing. A job offer to the person who swore never to go back to that city is a story.
It is concrete. A realisation is not an incident. "She understood that she had wasted her twenties" is interior; "her sister arrived with two suitcases" is an event. Interior turning points matter enormously, but they are consequences, not engines.
What it looks like in practice
In Pride and Prejudice, a wealthy single man takes the house next door. That is all — but it is irreversible in the small social world of the book, and it immediately makes five sisters' futures a live question. In The Hobbit, thirteen dwarves turn up uninvited at a comfortable man's door; the comfort is established first, precisely so the intrusion costs something. In Alice's Adventures in Wonderland, a rabbit in a waistcoat goes past and Alice follows — the incident and the choice in the same gesture. In Kafka's The Metamorphosis, the whole thing is in the first sentence, because the ordinary life is implied by how absurdly Gregor worries about being late for work.
Notice how small several of these are. Inciting incidents do not need to be catastrophes. They need to close a door.
Four ways drafts get it wrong
Too late. By far the most common. Three chapters of ordinary life, carefully built, and the story begins on page sixty. Readers do not have the patience that the writer, who already knows what is coming, imagines they have. The usual fix is not to write less setup but to move the incident earlier and let the ordinary life arrive around it.
Too small to close a door. Something happens, and the character could reasonably ignore it. Then the author has to invent a reason for them to care, and the reader feels the machinery.
It happens to someone else. A war breaks out, a king dies, a prophecy is announced — and your protagonist is a spectator. World events are context. The incident has to land on the person we are following.
It is buried. The event is there, in a subordinate clause, between two paragraphs of description. If readers cannot find the moment the story started, it did not start. Give it a scene.
Where it goes
Common advice puts it in the first ten to fifteen per cent of a novel, which is a reasonable default and nothing more. What matters is the ratio: enough ordinary life that the break registers, not so much that readers are waiting. Short fiction often has nothing else — in a very short story the inciting incident can be the first line and the rest is consequence. Serialised fiction pushes it earlier still, usually into the first chapter, for the simple reason that nobody is committed yet; that pressure is part of how to write your first chapter, and it interacts with everything in how to pace a novel.
If you cannot find yours
Open your draft and ask where a character first does something they could not have done in chapter one. That is often the real inciting incident, several chapters in, and the material before it is backstory you have been writing in the wrong order. The usual rescue is unglamorous: cut to that point, start there, and feed the earlier life back in as you go.
And if you genuinely cannot locate it, the problem may not be structural. Sometimes it means the character does not yet want anything badly enough for an event to threaten.
Serials make this measurable
Publishing a chapter at a time gives you something a finished manuscript cannot: you can see where readers arrive and where they stop. If the comments appear at chapter three and not chapter one, you have found out exactly where your story begins. We make Arwy, an Android app where books are published chapter by chapter and readers comment as they read. It will not plot your novel for you — for structural planning and outlining, use a proper writing tool and bring the chapters here.
Writing chapter by chapter? Readers will tell you exactly where your story starts. Arwy is on Google Play.