I had to explain to my mum some years ago - when someone offers you a lower price for CASH.
They mean that they are cheating the tax office and not declaring the income.
So they usually are:
- Not paying 1/11th GST
- Not paying income tax at their marginal tax rate (25% for company or usually 34.5% for sole traders between 45k-120k)
- Probably still claiming their expenses as normal.
So they are potentially TRIPLE CHEATING.
And given that a large portion of Tax raised goes towards the poor, aged, disabled or towards useful things like schools, hospitals, roads, etc. - in my opinon they are unAustralian. (I do respect differing points of view of course).
While the ATO doesn't catch everyone - there are a bunch of tools that they do have
Such as Small Business Benchmarks and
Personal Living Expenses Worksheet (below) to try to show that someone is not reporting their income