Some of these properties will be the sellers' main home so not liable for the tax and we estimate this to account for around 60 per cent of sales.
So 40 per cent of 8400 sales nationwide give us a total of almost 3400 properties that would be up for the tax.
Capital gain for properties shifted in less than two years is $230 million, taxed at an average rate of 30 per cent is almost $70 million a year to the taxman.
But not all capital gain will be liable as cost paid for renovations need to be taken into account. For example, if you bought an investment property for $500,000 and spent $50,000 renovating it, then sold it a year later for $600,000 you'd only be liable for capital gains tax on the $50,000 profit.
Some people will already be obeying the current tax laws and will be included in this amount, so again this figure will be scaled down.
Nick Goodall is a senior research analyst at CoreLogic.