Well and good, but tax is owed the Chinese coffers if you earn more than 4800 yuan a month, full stop. Whether your employer dodges paying your tax is a moot point. I have paid tax on occasion and my current employer is taking extra care to make sure I do not qualify for tax paying. He does so by paying my bonus in cash while my basic salary is trasnferred to my bank account, leaving tracks everywhere. It would look scurrilous if a public school of my employer's standing wouldn't pay enough for their teachers to have to return some of the money to the state...

Anyway, to satisfy the original poster's query: I used to get very good information from a website www.dezshira.com
Not sure if they provide this kind of information at this moment, though; I remember the tax kicked in at 5%, then 10, and rising quite quickly to over 20%.