RE:Can someone explainNo problem, you can buy and sell from either exchange. You can have tfsa-Canadian dollar account and tfsa-US dollar account. My recommendation....if you have tfsa-cdn $ account, then buy with ticker SONA-CSE because you will buy in canadian $. There are no US$ conversions. If you have US$ in tfsa-US dollar account, then buy from Nasdaq using the Sona ticker. Again, you won't be making any foreign exchange conversions.