Looks like a self-enforcing tax rate (comparable to price floor) has at least been proposed:

[...] have proposed having owners self-assess the value of their property under penalty of having to sell at this self-assessed value.111 This has the simultaneous effect of forcing truthful valuations for taxation and of forcing turnover of underutilized or monopolized assets to broader publics.

From https://plurality.net/read/5-7/