in many a place not having the tax to meet your liability is your problem. At the moment of the taxable transaction you did have the money to pay it. It's not the tax man's problem if it's subsequently been lost or bet elsewhere since or more likely the overall value has just gone down.

Each country will have a different approach so there's no point in listening to anyone other than a tax professional trained in Austria. There may well be a simple way of dealing with it.