As verbs the difference between cess and cass
is that
cess is (british|ireland) to levy a or
cess can be (obsolete) to cease; to neglect while
cass is (obsolete|transitive) to render useless or void; to annul; to reject; to send away.
As a noun cess
is (british|ireland) an assessed tax or
cess can be (rail transport) the area along either side of a railroad track which is kept at a lower level than the sleeper bottom, in order to provide drainage.