Hi Sk3tchy,
An accountant can help you maximise your legitimate tax deductions and lodge your return.
In regards to tax, there are two good things Offsets and Deductions.
Deductions will reduce your taxable income. Offsets reduce the actual amount of tax you pay (Ie, $100 of deductions will reduce your tax by $30 if your on a 30% Marginal Tax Rate [MTR] compared to $100 of offsets will reduce your tax by $100). Tax Offsets used to be called Tax Rebates.
Depending on how your business acquires a vehicle can also affect the tax, eg, if your business buys a vehicle it is a capital acquisition which can be depreciated over the useful lifetime of the vehicle vs if you leased a vehicle the whole cost is an expense to the business and hence all deductible (this is why it's really popular to rent properties, computers and other business assets and it's generally more cashflow efficient).
Not sure where you got the idea of GST being paid on SGC.
GST is a tax added to the Goods and Services you charge clients or customers, eg, if I charged a client a fee, we have to add 10% GST (which goes to the tax office).
SGC is Superannuation Guarantee Contributions which is compulsorily for Employers to pay on behalf of Employees (see
Superannuation), this needs to be paid for employees which earn more than $450 per month ($5,400 pa which is inline with previous 0% tax rates, now the 0% tax bracket is $6,000).
For self-employed the options are a bit more flexible, when to pay and you can lump it up to reduce taxable income before the end of financial year.
Similarly to being employed, a deductible contribution will reduce a business or self-employed taxable income and only get taxed at the contributions tax rate of 15% (vs the business tax rate of 30% [this means you save 15%] or your MTR if your self-employed [up to 30% savings!!!]).
Sole traders mean that you are responsible and LIABLE for all of the business debts and profits which are taxed at your MTR.
A business structure means that the business is it's own entity. Also all profits are taxed at 30% compared (say on a profit of $30,000, tax $9,000) compared to a sole trader made $30,000 they only pay $3,960 ($0 to $6,000 tax free [if an Australian resident] and then 16.5% up to $30,000 [including Medicare Levy 16.5% x $24,000]).
You should read
business.gov.au home page which can help you a bit more.
For business structures see
Decide on a business structure
Cheers,
Dan
PS Before doing anything speak to your accountant!