Track adjusted cost base across every account you hold
Adjusted cost base is not a number you calculate once. It is a record you keep, through reinvested distributions, return of capital, transfers between institutions and corporate actions, for as long as you hold the security and six years after you sell it. Luum keeps that record across every account and brokerage, pooled per taxpayer the way the CRA requires.
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Calculating it once is the easy part
The arithmetic of an average cost pool is simple enough to do by hand. What breaks a cost-base record is not the formula, it is the four years of events nobody applied to it.
Pooled per taxpayer, not per account
The same ETF at two brokers shares one average cost, so neither broker’s figure is yours. See cost base across two brokerages.
Return of capital, applied in the right year
It lowers your cost base instead of being taxed, and it is confirmed on a T3 after year end. Return of capital and your cost base covers why it accumulates unnoticed.
Transfers that arrive without their history
A transfer is never a disposition, but the cost often arrives estimated, reset to the transfer-date price, or missing entirely. Entering the original cost is what repairs it.
Two currencies, converted per transaction
A US-listed holding’s cost base is assembled from the rate on each purchase date. One conversion at today’s rate produces a different and wrong number.
What your broker’s number is, and is not
Every brokerage shows a book value, and box 20 of your T5008 carries one labelled cost or book value. Both are honest attempts made from one institution’s records, and the CRA tells the brokers preparing that slip, in as many words, that the figure may not reflect your adjusted cost base. The number on your return is yours, and so is the liability if it is wrong. T5008 box 20 is not your adjusted cost base works through the four places it comes apart.
Where to go next
- The adjusted cost base calculator runs one security’s pool in your browser, with nothing stored, if you want the arithmetic before the record.
- Adjusted cost base, explained covers the mechanic itself, with a worked example.
- How Luum tracks adjusted cost base states which adjustments are applied automatically and which are left to you.
- Luum vs AdjustedCostBase.ca is the honest comparison against the dedicated tool, including the superficial loss rule it applies and Luum only flags.
Common questions
- What is the difference between an ACB calculator and an ACB tracker?
- A calculator answers one question once: given these purchases, what is the average cost of this security today. A tracker keeps that answer correct over years, as distributions reinvest, as return of capital lowers the base, as positions transfer between institutions and as corporate actions reallocate cost. Most people do not have an arithmetic problem. They have a record that stopped being maintained several years ago.
- Why can my brokerage not track adjusted cost base for me?
- Because it can only see its own accounts. The CRA pools identical property per taxpayer rather than per account, so the same ETF held at two institutions shares one average cost that neither broker can compute. Your broker reports a book value for the account it holds, and the CRA tells brokers preparing a T5008 in as many words that the figure may not reflect your ACB.
- Does it handle return of capital?
- Yes. Return of capital reduces adjusted cost base rather than being taxed when received, and Luum reads distributions by type and applies the reduction. This is the adjustment most often missed, because it is confirmed on a T3 slip after year end rather than on the statement that showed the payment.
- What about holdings I transferred in from another broker?
- A transfer is not a disposition, so the original cost base should follow the shares. In practice it is often estimated, reset to the transfer-date price, or lost, which is why a transferred-in position is the most common source of a wrong cost base. You can enter the original cost so the pool is built from what you actually paid rather than from what arrived.
- Can I use it for more than one account?
- That is the case it exists for. Accounts are kept distinct for tax treatment while identical property is pooled across all of them for cost base, which is the combination a single brokerage cannot produce and a per-account spreadsheet gets wrong by construction.
- Does it track the superficial loss rule?
- It flags it, and it does not apply it. When a sale at a loss sits within 30 days of a purchase of the same security in the accounts on your report, the Tax Centre marks the sale and estimates the loss that may be denied. Your gains and your cost base stay as they are, because the rule also counts purchases Luum cannot see, such as one in a spouse’s account. If that rule is central to how you manage a taxable account, read the comparison page that covers a tool which does apply it.
Keep the record, not just the answer
Starter is free forever. No credit card required.