You need to report each "sale", so Yes, you will calculate the ACB for each trade. If you buy and sell that particular stock entirely, it's easy to calculate. For example:
- If you buy 300 shares @10.00ea + 200 shares @12.00ea, then sell 500 shares, your ACB is 5400.00 or 10.80per share. Report this "sell".
- If you buy another 400 shares of the same @10.00 and sell those 400, you report another "sell".
It's when you don't completely sell the stock that it get's a little more complicated. CRA requires you to keep a running total of the Adjusted Cost Base (ACB) for tax purposes. When you buy shares, the total ACB is recalculated to be the previous total ACB, plus the total cost of the new shares.
