GST does catch the tax avoiders in the tax net to some extent. Broadening the tax base.
Some things need to happen for a fairer tax system.
Capital gains tax.
Currency speculation taxes. Needs other countries to implement at the same time to work.
45% on really high incomes. Over $150k.
Get rid of trusts and other dodges.
Except for taxes on high wage earners are all means of broadening the tax base.
For income taxes I would like to see Gareth Morgans idea of a universal individual minimum income administered through IRD replacing benefits. The main advantage is reducing administration costs, but it also removes the need to go and beg to WINZ for a benefit.