I recently became a resident of the US. I was formerly a resident of the UK. I transferred my stocks and shares from the UK to a US broker shortly after I moved.
I understand that when selling these stocks my cost basis for tax purposes is the value from when I originally brought them back in the UK.
However some of these stocks, brought around 2011 were originally placed into an ISA account. A couple of years later around 2013 I transferred them out of the ISA into a normal brokerage account.
For the stocks which were originally held in my ISA, I am unclear if the cost basis for US tax purposes is the value of initial purchase, or the value when they were transferred out of the ISA account?
I cannot find clear information of this, as normally for UK taxes stocks held in an ISA are capital gains immune and the cost basis is only created when they are moved out of the account but it is unclear to me if the IRS respects this rule for those who become residents of the US. (If it is important I became a US resident after moving the stocks out of the ISA).