Informal:
* Got ya: This is the most common spelling in informal contexts, used to indicate that someone has been tricked or caught out.
* Gotcha: This is another common spelling, often used in the same way as "got ya."
* Got you: This is a more formal spelling, still used in informal contexts but with a slightly different connotation. It can be used to express understanding or agreement, or to playfully tease someone.
Formal:
* Got you: This is the most formal spelling and is used in writing and formal speech. It is typically used to express understanding or agreement.
Ultimately, the best spelling depends on the specific situation and your intended meaning.