I got feedback from Trading212 user who claim that he got the correct double taxation treatment for his US stocks (the dividend is $0.233, after 10% tax it should be $0.2097, he received 2 cents for 1/10 part of a share, however it says “amount per share $0.21”).
Because the correct tax rate for Bulgaria was applied this means that there is some information about the tax residency of the owner of the stock.
When I asked IB and Trading212 support they both answered to my question incorrectly citing 15% tax rate, but this is not true, the tax rate according to the double taxation treaty between US and Bulgaria is 10%, and in practice it looks like it’s the 10%.
Proof:
(The screenshot is from another customer’s account, I still don’t own US stocks.)
Currently there are more important issues, like this for example.