a special high rate of tax paid by people or companies with a high level of income:
supertax on
• The government is likely to punish big organizations by introducing a supertax on their profits.
— compare surtax* * *
supertax UK US /ˈsuːpəˌtæks/ noun [C or U] TAX
► a very high rate of income tax or company tax paid by those with a very high level of income or profit: »
Introducing a new supertax could help to make up the deficit in the public spending budget.
Financial and business terms. 2012.