Free Adjusted Cost Base (ACB) Calculator for Canadian Investors

Adjusted Cost Base (ACB) is a Canadian tax concept that represents the true cost of acquiring an investment. It is the starting point for calculating capital gains or capital losses when you eventually sell. Getting ACB right matters because the CRA taxes you on the difference between your selling price and your ACB, not the original sticker price.

ACB starts with the purchase price of your shares but it does not stop there. You add any commissions or trading fees paid to your broker on the buy. If your ETF or mutual fund distributed a return of capital (ROC), that amount reduces your ACB because it is a tax-free return of your own money. Reinvested distributions that you reported as income increase your ACB so you are not taxed twice on the same dollars.

Canada uses the weighted average method for calculating ACB on identical securities. Unlike the US, where you can choose specific lots (FIFO, LIFO, specific identification), Canadian investors must average the cost of all shares of the same security held in the same account type. If you hold 100 shares bought at $25 and later buy 50 shares at $30, your new ACB per share is ($2,500 + $1,500) / 150 = $26.67 regardless of which lot you sell first.

Corporate actions like stock splits, mergers, and spin-offs also adjust your ACB. A 2-for-1 split doubles your shares and halves your ACB per share, keeping the total the same. Mergers may require you to allocate ACB between the acquiring company and any cash or other consideration received. These adjustments are easy to miss and can create errors that compound over years of investing.

Tracking ACB manually becomes unmanageable once you hold more than a handful of positions across multiple accounts. Every buy, every distribution, every corporate action needs to be recorded. This is exactly the problem WealthWatch solves: it imports your transactions from all your Canadian brokerages and computes ACB automatically, in real time, with an audit trail for every adjustment.

The superficial loss rule (ITA section 54) is one of the most misunderstood areas of Canadian tax law for investors. It kicks in when you sell a security at a loss and then you or an affiliated person (spouse, corporation you control, RRSP, TFSA) repurchases the same or identical property within 30 calendar days before or after the sale, and the property is still held at the end of that 61-day window.

When a superficial loss is triggered, you cannot claim the capital loss on your tax return for that year. However, the denied loss is not gone forever. It gets added to the ACB of the repurchased shares, effectively deferring the tax benefit until a future sale. For example, if you sell 100 shares at a $500 loss and repurchase them the next week, the $500 loss is denied but your ACB on the new shares increases by $500. When you eventually sell without triggering the rule again, the higher ACB results in a smaller gain (or larger loss), so you get the benefit then.

Common pitfalls include: buying in your TFSA within 30 days of selling at a loss in your taxable account (the loss is permanently denied because TFSA gains are tax-free), DRIP purchases that fall within the window, and failing to account for your spouse's transactions. WealthWatch flags potential superficial losses by monitoring the 61-day window across all your connected accounts, including registered accounts, so you can make informed decisions before triggering the rule.