Average Cost Base. the ACB of a mutual is determined by averaging the price of all units of a fund an investor holds, including those purchased with reinvested distributions. The ACB becomes the cost basis for determing a capital gain or loss when units are sold.
Adjusted Cost Base. When you sell a capital property, your capital gain or loss for income tax purposes is calculated as your proceeds of disposition less your adjusted cost base (ACB) and any outlays or expenses relating to the disposition. In the case of shares acquired on the open market, your ACB is normally the cost of the shares plus any brokerage fees relating to the acquisition. In the case where shares have been acquired through the exercise of stock options, the ACB is adjusted by the taxable benefit associated with the exercise. The ACB per share will be affected by stock splits and stock consolidations. In addition, where identical properties (such as shares of a particular class in a public company) are held, the ACB per share is determined as the average over all those properties. The ACB is also affected by any capital returned to an investor.