Så här står det på visainchina.com:
Q10. If my visa expired and overstay in Shanghai, what can I do and how much fine should I pay?
A: As the Chinese immigration law, if your visa expired less than 10 days, it's not necessary to pay any fine, you have to go to the immigration office, the officer will ask some questiones and put down your words in writing and make a record. They will also notice you don't break that again. If your visa expired more than 10 days, they will charge you fine, the fine is 500RMB per day except the first 10 days, and the maxmium is 5000RMB. for example, if you overstay 12 days, they will charge (12-10)*500=1000RMB. Following are the contact information of immigration office, you can go to there when your visa expired:
Men självklart ska jag kolla upp det närmre.