I have a modest investment in a US stock, purchased recently for purposes other than investment although I hope not to lose money on it. I am likely to sell the shares in a year or two. I think the broker(Revolut) will, I presume, withhold 15% or 30% tax. If the shares show a gain, it will be well below my annual threshold of €1,270. How would I get the withheld tax back or is it lost?