Ann: Appointment of Administrators, page-26

I'm not a taxation or bankruptcy lawyer however my understanding is that you can only claim a tax loss once the company is officially wound up.

You are still a shareholder and you have not sold your shares, therefore triggering a cgt event.

Sorry to burst your bubble but unless you can find someone to buy your shares off you (and I'm not certain even of the legalities behind that) then it could take a year or two or more for the company to be wound up before you can claim that tax loss.

Speak to your accountant.

Best of luck to those that have taken a hit.