There are arguments in favour of a 100% inheritance tax. For example, we could look to John Rawls and the argument from behind the veil of ignorance. If we didn’t know where we would arrive in that lucky sperm club lottery wouldn’t we prefer a society in which starting points were equal? So, tax inheritances at 100% and then distribute that wealth as a starting grant perhaps.
However, the idea does seem to fail on two points. The first is that while it’s true that we can’t take it with us, therefore this could be seen as a “fair” tax, that people will fight, struggle and even lie to be able to provide an inheritance to their children does rather militate against the idea that people do see it as a fair tax. Peoples’ actions do seem at odds with that particular result of that particular blend of moral reasoning.
But much more importantly we’ve evidence that such a system is not efficient. For we’ve had societies that did effectively have 100% inheritance taxes: and those societies failed precisely because they did.
Both Mamluk Egypt and the Ottoman Empire worked on the basis that whatever was accumulated during the lifetime of the elite (with the Mamluks, generals, with the Ottomans, Pashas) in the way of property, businesses, land and so on, was theirs for life and only for life. When they popped off those estates, however grand or vast they were, were distributed to the next generation of generals and pashas. With the Mamluks the children of the generals were, as they had not been recruited as military slaves from the steppes, specifically barred from even attempting to join that next generation of the elite.
This led to a certain short termism in how such properties were managed: having reached the top there would be, at most, a couple of decades to enjoy the wealth. Nothing could be passed down to the next generation. Thus, don’t invest in anything, simply extract. Societies in which we do have 100% inheritance taxes therefore seem to become extractive ones, not investing ones. With all of the obvious connotations for the living standards of the subsequent generations. To say nothing of the current living standards of the peasantry being extracted from.
Whatever the philosophy here we have tried it as a species and it really just doesn’t seem to work.