He might get a fine. In most fictional worlds that mirror the real world to some extent, not filing taxes usually leads to financial penalties.
He could face fines. Just like in the real world, not filing taxes usually results in financial penalties. In the fanfic, these fines could put a strain on his finances, especially if he's not expecting them.
In the fanfic, if Harry doesn't pay taxes, he might face legal troubles. The authorities could come after him, perhaps freezing his assets. He could also lose his reputation in the wizarding community, as it's an unethical act.
Taxes in Harry Potter fanfic might not be a common theme, but they could add an interesting layer of realism. If there are taxes on magic use, it could lead to some characters having to find ways around it or deal with the consequences of not paying. Maybe certain spells are taxed depending on their power or rarity, which could create conflicts between wizards who use more powerful magic and those who can't afford to pay the tax.
Maybe he simply forgot. In some fanfics, characters can be scatter - brained and overlook important things like filing taxes.
One way is to create a new Ministry department that deals with magical taxes. You could write about how this department audits wizarding businesses. For example, Ollivander's wand shop might be audited for taxes on the sales of wands. Another way is to introduce a tax on magical creatures. Hagrid might have to deal with the new tax regulations for his care of magical creatures at Hogwarts.
The plot could develop with the tax collectors in the wizarding world starting an investigation. Harry would then have to find a way to either prove his innocence or deal with the consequences.
One consequence could be the destruction of the friendship group. Ron, for instance, would be devastated. He has strong bonds with both Hermione and Harry. His reaction could range from seeking revenge on Hermione to falling into a deep depression. Also, the wizarding world as a whole would be in chaos. Harry was seen as the 'Chosen One', so his death would leave a power vacuum.
One consequence is that Harry may lose trust in Dumbledore. In fanfic, this can lead to Harry making decisions on his own, without relying on Dumbledore's guidance. For example, he might go off on his own to search for answers about his parents' death or Voldemort's secrets.
One consequence could be that the story takes a different turn. Instead of the typical heroic plot, there might be a more character - centered exploration. Others around him may have to step up and fill the void. For example, his friends might become the heroes instead.
On the other hand, not competing might lead him to find alternative paths. He could start his own non - competitive projects or groups, which could have a big impact on the fanfic's community in a different way. For example, he could form a study group for magic that focuses on sharing knowledge rather than competing for grades or status.