The line between taxes and takings is VERY difficult to draw and to define. But that difficulty doesn't mean that the distinction isn't one that is important and deserves careful consideration.
Some of the earmarks of taxes that distinguish it from a takings are:
- the existence of a taxable "event": such as earning income, buying goods and services, dying, selling assets, making a gift, etc.
- Uniformity: Meaning that the tax exists in the same way for all payers across the board, even though the structure of the tax might exclude certain people by applying floors and minimums.
- Generality: This is closely related to uniformity but adds the element of sharing the burden. When the government takes a strip of property to build a road, that is a taking because there is no general burden. When the government levies a property tax to build the road, there is a general burden and that is a tax.
The property tax presents an interesting question. First of all, property taxes have a long history going back hundreds of years. Taxing property was the primary way to finance government long before the US was a country. So there is a long tradition which counts for something. Second, property taxes have no exceptions based upon individual circumstances. It's levied on ALL property of a given class. Third, there is no personal obligation to pay property taxes. You can go to jail for not paying income tax. You can't go to jail for not paying property tax. But I agree, the question of property tax is a difficult one.
In the case of a wealth tax, there is no "event" to trigger a tax obligation. I thought that feature of a tax was fairly clear prior to Chief Justice Robert's AHCA opinion. But he didn't obliterate that feature as he said the penalty is a tax. I think no "event" for a wealth tax suggests it is a confiscation, not a tax. A practical reason to oppose a wealth tax is the enormous cost of compliance for both the payor and the government. Inheritance tax is essentially a wealth tax triggered by the event of dying. Because most assets are not easily valued bank accounts or listed securities, but property, the value of the wealth is determined only by opinion. No two appraisers will agree on a property's value and the cost to determine wealth is significant.
In sum, I think a wealth tax is a terrible idea in addition to its serious constitutional limitations. I think the notion of a wealth tax are mostly motivated by base lefty emotions involving schadenfreude, not by practicality and common sense.