SUPERTAX

surtax, supertax

(noun) an additional tax on certain kinds of income that has already been taxed

Source: WordNet® 3.1

Etymology

Noun

supertax (plural supertaxes)

An additional tax on something that has already been taxed

A higher rate of an existing tax

Source: Wiktionary

Su"per*tax`, n. [Super- + tax.]

Definition: A tax in addition to the usual or normal tax; specif., in the United Kingdom, an income tax of sixpence for every pound in addition to the normal income tax of one shilling and twopence for every pound, imposed, by the Finance Act of 1909-1910 (c. 8, ss 66, 72), on the amount by which the income of any person exceeds £3,000 when his total income exceeds £5,000.

Source: Webster’s Unabridged Dictionary 1913 Edition