I want to buy a loaded casacius coin 1.1 btc. If I purchase it and the seller most likely sells my btc
The following day. Would I pay capital gains tax on the 1.1 or does the buyer pay it real confused not a tax person.
No idea where your jurisdiction is.
But for most countries, this will not be a taxable event until you sell.
The only thing that you need to be aware of when you buy the physical coin is your cost basis. That will determine what your CGT liabilities are going into the future when you do decide to sell. But the CGT liability is not predetermined in any way.