I had it removed off of most things but so many places require it. Thankfully my cards have been printed without it.
It’s the FX changes in addition to the capital gains. If the property will have a mortgage, it’s usually renewed every two years. That mortgage renewal triggers the FX reporting. GBP is down against the dollar at the moment. If the rate becomes more favourable, it would give you a “gain” though on paper. That “gain” is taxable.
Easy example.
You purchase a house for £100k at 1.3 to 1 for the dollar. Therefore the house is valued at $130,000.
Two years from now you go to renew your mortgage. The house is still valued at £100k but the GBP to USD is now 2 to 1 (a girl can dream). Your house is now worth $200,000.
US tax now says you’ve made $70,000 in capital gains and you owe tax on that $70k. But you still just have your house - no actual cash.