If the company asks you to pay a penalty (违约金) when you leave, first see which kind it is: only the service period for specialized training and a non-compete restriction can carry a penalty, and the law does not allow one under any other name

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In plain words

If the contract says "pay money if you leave early," the law allows this in only two situations: the company paid for you to take specialized technical training, or a non-compete restriction (竞业限制). If there really was specialized training, the money you pay can't exceed the training cost, and it has to be prorated by the part of the service period you haven't worked.

Mentioned in

If you signed a non-compete, and the company doesn't pay the monthly compensation after you leave, send a written demand; after 3 months without payment you can terminate it; for a post that never touched trade secrets, you can ask that the clause be declared ineffective

Translated from the Chinese original. Original book, section 19, tip 22. This section describes legal rules, mostly mainland China’s. It is general information, not legal advice; for your own case, talk to a lawyer. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer