I held some stock in Australia for 14 years and 4 months that has enjoyed some healthy long term capital gains in that time.
Recently I became a US Resident for Tax Purposes under the Substantial Presence Test (before this I have never been a US resident for tax purposes).
I sold the above stock 10 days after becoming a US Resident for Tax Purposes.
Can the cost-base be calculated using the market value at the time I became a US Resident for tax purposes? Or is it the original cost basis from 14 years ago?
Do you know of any public documentation that refers to this situation of a capital gain where most of the gain happened before becoming a US Resident? In my case, I was not a US Resident for 99.8% of the ownership time of this asset.