term:

Stamp

stamp n

: an official mark or seal set on something (as a deed) chargeable with a government or state duty or tax or on papers requiring execution under certain conditions to signify that the duty or tax has been paid or the condition fulfilled
;esp
: revenue stamp

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.