The extract in inverted commas below has been taken from a guide compiled by the American Citizen Services Office, U.S. Embassy, Beijing - http://beijing.usembassy-china.org.cn/teach.html

"Residence Permits

In addition to a valid passport and visa, all prospective teachers must obtain a Residency Permit within thirty days of their entry into China. One may not legally teach in China without both the Z visa and a valid Resident Permit. This is necessary whether one is classified as a foreign teacher or a foreign expert. Employers should provide assistance in obtaining this document."

Contrary to what some China old hands say, be aware that any Chinese employer who expects you to teach before he has gotten and given you your Residence Permit is putting pressure on you to teach illegally. Unfortunately, there are many such employers in China!