expression
Compensation for work performed beyond regular hours, as defined by labor standards.
今月の時間外手当ては予想より多かった。
This month's overtime pay was more than I expected.
残業代 is a more casual, everyday term for overtime pay, while 時間外手当て is a formal term often used in legal or HR contexts.
Compound of 時間外 (outside regular hours) + 手当て (allowance, pay).