Mipik

I have been living here for 7 months.
All this time I had some money in US$ in bank account overseas.

With the change of the exchange rate this money obviously would be much less A$ now than 7 months ago.

So the question is: can I declare this money at the end of tax year and use it as a loss to reduce the amount of my tax due (offset against my earnings)?
Any limits?

Centurion

Whilst not professional advice, I would say not. You have had funds in an overseas account, the capital of which at the time you became an Australian tax resident is not subject to tax. However, any interest gains you may have received are liable for taxation as Australia taxes on worldwide income from the time you became a taxapayer.

The relative value of the AU dollar between now and then I dont think has anything at all to do with your tax liability at all and I dont believe you can offset that "loss" since it was not a loss actually suffered.

As to when someone buys a currency is entirely up to them.