It is my intention to list here only the stamps that were overprinted for postal use of one kind or another.
Note that special kinds of postage stamps (postage due, parcel, airmail, charity (part of value pays the postage), express and registered stamps) are mixed into the main catalogue list, but can be viewed separately here.
Non postal stamps can be categorised into:
Stamps produced for postal use, but never actually issued as such.
Stamps produced to show payment of tax.
Stamps produced to send money, usually from one post office to another.
Stamps produced for propaganda or commemorative reasons with no postal value.
Stamps produced to raise funds for charity, with no postal value; not altered to postage stamps in China.
Christmas or other special occasion labels; not altered to postage stamps in China.
There is only one Chinese postage stamp that was made by overprinting a propaganda label - the Communist postal overprint on the Japanese label commemorating the 2,600th anniversary of the Japanese Empire.
No charity or special occasion labels were ever overprinted for postal use (at least in China).
Most Chinese savings stamps were postage stamps overprinted for savings use and none were altered for postal use.
So the only other categories used are the unissued stamps, revenue stamps and money order stamps.