Adjusted Cost Base (ACB) is the foundation of capital gains tax calculation in Canada. Unlike the US where FIFO or specific identification methods are common, Canada uses the average cost method for most securities. This guide walks through detailed examples of ACB calculation for common scenarios.
Basic ACB Calculation
ACB tracks the total cost of your investment, including the purchase price and any associated costs such as commissions. When you buy shares, you add to the total ACB. When you sell, you use the ACB per share (total ACB divided by total shares held) to calculate your capital gain or loss.
Example: Multiple Purchases
January: Buy 100 shares of XYZ at $20 ($2,000) + $9.99 commission = $2,009.99 total ACB. March: Buy 50 more shares of XYZ at $25 ($1,250) + $9.99 commission = $1,259.99. New total ACB = $2,009.99 + $1,259.99 = $3,269.98 for 150 shares. ACB per share = $3,269.98 / 150 = $21.80.
June: Sell 75 shares at $30. Proceeds = 75 x $30 = $2,250. Cost = 75 x $21.80 = $1,635. Capital gain = $2,250 - $1,635 = $615. Remaining ACB = $3,269.98 - $1,635 = $1,634.98 for 75 shares (still $21.80 per share).
ACB With DRIP Reinvestments
Each DRIP purchase adds to your total ACB. If XYZ pays a $0.50 quarterly dividend and you hold 100 shares, that is $50 in dividends. If the reinvestment price is $22, you receive approximately 2.27 shares. The $50 is added to your total ACB, and 2.27 shares are added to your total shares. This changes the ACB per share slightly.
ACB With Return of Capital
Return of Capital (ROC) distributions reduce your ACB without creating an immediate taxable event. If you receive a $2 per share ROC distribution on 100 shares, your ACB decreases by $200. If your ACB goes below zero, the negative amount becomes a capital gain in that year.
ACB With Stock Splits
A 2-for-1 stock split doubles your shares but halves the ACB per share. Your total ACB remains the same. For example, 100 shares with a total ACB of $2,000 becomes 200 shares with a total ACB of $2,000 (ACB per share goes from $20 to $10).
Common ACB Mistakes
- Forgetting to include commissions in the ACB calculation.
- Not adjusting ACB for return of capital distributions.
- Using the wrong exchange rate for US-denominated securities in non-registered accounts.
- Not carrying ACB forward when transferring shares between brokerages.
- Treating each tax lot separately instead of using the average cost method (which is required in Canada for most securities).
Disclaimer: This article is for informational purposes only and does not constitute tax advice. ACB calculations have many nuances including superficial loss rules, corporate actions, and currency conversion requirements. All examples are simplified. Consult a qualified tax professional for your specific situation.
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