Supertax

[Sarah]

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

[Kit]

An additional tax on something already taxed; a surtax.

[Lanell]

a very high rate of income tax or company tax paid by those with a very high level of income or profit: