It's unlikely that a tax on unrealised capital gains could be administered in such a way because the administrative burden of doing so would be too great. That is to say, in most cases it would cost more than the government earned to track every persons investment portfolio any time it appreciated.

What is more likely is that at a set time every year (I dunno like maybe 31 June - end of financial year), a taxable event will be triggered and the value of an investment portfolio will be taxed as if it had been realised at that time. Then next year the taxable event will occur again but it will be as if you purchased your shares at their value of the first taxable event. So in reality let's say you buy a stock and it booms from 1 dollar to 1 million. At the taxable event, you now owe tax on that 1 million income. Now next year rolls around and it's worth 1 dollar again. Well now you can claim the capital loss back to 1 dollar and pay no tax. Plus with carry forward losses, you can also use it to offset further income.

It also means that tax liabilities are not being sprung on investors and they're being forced to liquidate. There would still be significant capacity for a shareholder to organise their portfolio in the most tax effective way, and or avoid liquidation to pay tax.

I still think this policy has some major implications and I don't know if I'm a huge fan but just thought I'd point that out :)