The issue of paying tax in China has suddenly reared it's ugly head! Well, for ME at least!

Maybe I'm just lucky, but out of six schools that I've worked for in China I've only so far payed tax in the one private school that I worked in. Now, two schools that I'm considering working for state that I will have to pay tax, and one of them is a government school (although I'm not sure if that has any relevance). So, could anybody answer the following questions?:

1.What amount can a foreign teacher in China earn a month, before being taxed?

2.After that amount has been exceeded, what percentage of tax has to be paid by FTs?

3.Can schools legally tax us on money earned from overtime work?

4. Is there a clear national law regarding this issue that transcends provincial boundaries?

5. Are tax laws regarding foreign workers being changed or are they just being more stringently enforced?

Quite a few for you! Yes I'm quite naive on this subject (paying tax is neither a hobby or habit of mine), so I really need some help. If anybody can answer any of the above it would be appreciated. I know it's a pretty boring subject, but I think if all FTs new the answers to the above questions it would be of great practical help!

Cheers!

Yingwen