Something i've been asking myself. Say you buy a house in only bitcoin without paying taxes on it, followed by a visit from the IRS. You say you bought the house in bitcoin, what can they do? Can they throw you in jail or fine you for that since you used an "erschatz" currency?
They can claim taxes. Not paying due taxes can lead to incarceration.
If you have some of your money in another currency and buy something with it, I don't think capital gains would be involved. This is a question for a lawyer but I can't imagine countries, banks, etc. who have their money in other currencies, must pay capital gains on things for purchases made.
I was under the understanding that taxes are paid when going from currency to currency (depending on country). Here in Germany you have no capital gains on BTC's held for over one year.
IAS
buying a house, especially if its a second house... you'll get tax... you can try to pay with bitcoin at never declare it... idk i wouldn't...