"The employer has not worked."
Translation:고용주는 일한 적이 없어요.
-ㄴ 적이 있다/없다 = to have done/to have not done something.
그 영화 본 적이 없어 = I haven't seen that movie.
아이슬란드 간 적이 있어? = Have you been to Iceland?
It kind of means "experience". So literally, the employer doesn't have work doing experience.