Question about taxes

Trying to decide whether it makes more sense to leave my job in November or December.

Is income tax based on when you WORK or when you get PAID?

Everything I am reading says it's based on income "earned" in a calendar year, but I'm not clear when it's considered "earned"– if I work in December and get paid in January, will that count toward 2025 or 2026 taxes?

by AgentSuccessful11