Example, In the beginning of 2016, I was purchasing in the price range of $1.30 to $1.60.
I still have shares long at those prices. If I get out of BPMX for anything less, it's a tax write-off from that purchase price on those lots.
If greatness happens and BPMX has a buyout at $3.00, then I only pay capital gain taxes above that $1.30-$1.60 range and because I've held for more than a year, I only pay around 15% on that.
So I keep a healthy old chunk of shares sitting long, and flip with my new shares to keep building.
TD shows your lot transaction history under "unrealised gain/loss". There it will give you the dates on when you're short shares will turn long.