O que acontece se você aparatar sem uma licença?

Não pode haver nenhuma maneira de detectar a Aparição sem uma licença.

Pela simples razão de que Harry aparatou várias vezes em HP e as Relíquias da Morte sem licença: ele era jovem demais para ter uma quando Ron e Hermione fizeram seus testes. Na verdade, ele até aparatou sem ser detectado em HP e o Enigma do Príncipe , quando pegou um Dumbledore enfraquecido da caverna do mar de volta a Hogwarts.

Mas se você fizer ser pego fazendo isso, você será multado.

"You have to pass a test to Apparate?" Harry asked.

"Oh yes," said Mr Weasley, tucking the tickets safely into the back pocket of his jeans. "The Department of Magical transportation had to fine a couple of people the other day for Apparating without a licence. It's not easy, Apparition, and when it's not done properly it can lead to nasty complications. This pair I'm talking about went and splinched themselves."

[...]

Harry had a sudden vision of a pair of legs and an eyeball lying abandoned on the pavement of Privet Drive.

"Were they OK?" he asked, startled.

"Oh yes," said Mr Weasley matter-of-factly. "But they got a heavy fine, and I don't think they'll be trying it again in a hurry. You don't mess around with Apparition."

_{-- HP and the Goblet of Fire}

Uma coisa que podemos dizer é que, se você aparatar sem licença (uma prática perigosa de qualquer maneira, evitada mesmo por muitos bruxos e bruxas totalmente qualificados), é bem provável que você faça uma bagunça disso mais cedo ou mais tarde. E quando o fizer, você pode se ver em apuros e precisar de assistência do Ministério da Magia ... que irá multá-lo:

'You have to pass a test to Apparate?' Harry asked.

'Oh yes,' said Mr Weasley, tucking the tickets safely into the back pocket of his jeans. 'The Department of Magical Transportation had to fine a couple of people the other day for Apparating without a licence. It's not easy, Apparition, and when it's not done properly it can lead to nasty complications. This pair I'm talking about went and splinched themselves.'

...

'They left half of themselves behind,' said Mr Weasley, now spooning large amounts of treacle onto his porridge. 'So, of course, they were stuck. Couldn't move either way. Had to wait for the Accidental Magic Reversal Squad to sort them out. Meant a fair old bit of paperwork, I can tell you, what with the Muggles who spotted the body parts they'd left behind ...'

Harry Potter and the Goblet of Fire - p.63 - Bloomsbury - Chapter 6, The Portkey