When NOT to Use It: You would not use
上任 (shàngrèn) for a regular, non-managerial job. For starting a job as an engineer, a teacher, or a salesperson, you would use
入职 (rùzhí - to be onboarded) or simply说
开始工作 (kāishǐ gōngzuò - to start working). Using
上任 for a junior position would sound strange and overly dramatic.