a) The obvious one - if you're over 60, come 1 July this year the new "simple super" legislation will make all income coming to you from your superannuation fund tax exempt - it doesn't even have to be included on any tax return you fill in. Hence retirees with adequate retirement savings will easily be able to pay no tax on a $100,000 annual income if it's coming to them from their taxed super fund.
b) If you're earning $100,000 salary in Australia the 2006/2007 tax rate for a resident single person would mean you normally would pay $27,850 in income tax (not counting the medicare levy), leaving $72,150 after tax income. This could be reduced to zero by arranging a salary sacrifice of %92,500 into superannuation. This would reduce your taxable income to $7,500. The tax rate on the first $6,000 of income is 0%, and the $235 low income tax offset would mean you could earn at least $7,500 taxable income without actually paying any income tax. Of course you'd probably need some other way to finance your living expenses if you reduced your taxable income to only $7,500! There is also the superannuation contribution tax of 15% on salary sacrificed contributions, so to some extent you'd simply be replacing $27,850 income tax with $13,875 contribution tax. This makes salary sacrifice of taxable income below $25,000 (the threshold for the 30% income tax rate) generally not worthwhile.
BTW This option would not longer be available after the new "simple super" rules come into force on 1 July - the max. salary sacrifice + SGL contribution total will be $50,000. And under the current rules, there is an age-based maximum that would make this option only work for older employees.
c) Have large tax deductions from investment interest expenses to reduce your taxable income to the extent that it entirely offset by franking credits from your stock dividends. This is theoretically possible, but would only be possible for some investors with large existing investment portfolios. For example,
Person X has a $1,000,000 stock portfolio yielding 3% ($30K) in fully franked dividends and earns $70,000 in salary. The stock portfolio averaging 6% capital growth.
If this person borrowed $2,000,000 via a margin loan at 8% interest and used it to expand the existing stock portfolio. The new situation would be:
$70K salary + $90K dividends.
Dividend franking credit $38,571.
Gross income = $198,571
Tax deductible interest = $160,000, paid for by salary and dividends.
Taxable income = 198,571 - 160,000 = 38,571
Tax on 38,571 = 6,921.30
Refund due = franking credit - tax liability = 38,571 - 6,921.30 = $31,649.70
The extra capital gain from the $2m extra invested is worth an average of $120,000. As it is eventually only taxed at half the applicable marginal income tax rate, the eventual after tax gain would be more than the decrease in current income.
Of course this would only work if you could live on $31K of after tax income, ie. you were going to invest $40,500 (56%!) of your after tax income anyhow. Otherwise you'd be short of income for living expenses.
Now, none of these options are practical or advisable for most people. And the ethics of paying nil tax is very personal - after all, someone has to pay for roads, schools, hospitals etc. And the use of gearing, especially using margin loans, increases risk - you may end up with investments that perform way below "average" during your holding period. But some combination of the above can be used to reduce the amount of income tax paid, provided you are currently spending less than you earn and are investing some "after tax" dollars.
There also some further benefits possible by lowering your taxable income - for example, reducing the amount of medicare levy payable, qualifying for the government superannuation co-contribution, and so forth. You have to be a bit careful if you are married with kids and getting some "family tax benefit" payments (A or B) - the rules for calculating income differ between the ATO and centrelink.
It's probably best to end with another catchy quotation - "tax reduction should not be the key factor behind any investment decision." After all, it's no good getting a big tax break on an investment that ends up worthless.
* ie. high pressure sales talk for an investment scheme