1) IRS agent 2) One demanding payment 3) Penalty imposer 4) Tax collector 
one who exacts; extortioner; claimer of rights
• (n.) One who exacts or demands by authority or right; hence, an extortioner; also, one unreasonably severe in injunctions or demands.
Ex·act'or noun [ Latin : confer French exacteur .] One who exacts or demands by authority or right; hence, an extortioner; also, one unreasonably severe in injunctions or demands. Jer. Taylor.