Adjusted Cost Base (ACB) in Canada: How to Calculate It (2026)

If you hold investments in a non-registered account, Adjusted Cost Base (ACB) is one of the most important tax concepts you need to understand. Get it wrong and you will either pay too much tax by overstating your gains, or underpay and face CRA scrutiny. This guide walks through exactly how ACB works, how to calculate it, and the common situations that complicate it — including DRIP, Return of Capital, foreign securities, and the superficial loss rule.

What Is Adjusted Cost Base?

Adjusted Cost Base is the Canada Revenue Agency’s term for the average cost of an investment for tax purposes. When you sell an investment in a taxable (non-registered) account, your capital gain or loss is calculated as:

Capital gain (or loss) = Proceeds of disposition − Adjusted Cost Base − Outlays and expenses

ACB is not simply the price you paid for your most recent purchase. Canada uses the weighted average method — every purchase you have ever made of a security is pooled together, and the ACB per share represents the average cost across the entire pool. This means you cannot choose to sell your “cheapest” shares first (as the FIFO method used in the US would allow) — every share in a given security has the same ACB per share at any given point in time.

ACB is only required for non-registered accounts. Investments inside a TFSA, RRSP, FHSA, RESP, or RRIF are not subject to capital gains tax, so tracking ACB for those accounts is unnecessary.

Basic ACB Calculation

The formula is straightforward for a single purchase:

ACB per share = (Purchase price x shares + commission) ÷ total shares

Single-purchase example

You buy 100 shares of a Canadian bank at $50.00 per share. Your broker charges a $10 commission.

The commission is always included in ACB. Over decades of investing, this small addition meaningfully reduces your taxable gains.

Multiple Purchases: Weighted Average in Practice

Most investors buy more of the same security over time — through monthly contributions, dollar-cost averaging, or taking advantage of dips. Each new purchase updates the weighted average ACB.

Example: Three purchases of the same ETF

After these three purchases, you own 250 shares with a total ACB of $12,280 and an ACB per share of $49.12 — regardless of which specific shares you bought at which prices.

Selling from this position

Six months later you sell 100 shares for $58 each ($5,800 proceeds):

The ACB per share ($49.12) does not change after a partial sale — only the total ACB decreases proportionally.

DRIP: The ACB Complication Most Investors Miss

A Dividend Reinvestment Plan (DRIP) automatically uses your dividend payments to purchase additional shares instead of depositing cash. DRIPs are a powerful compounding tool — but they create an ACB headache that catches many investors off-guard.

How DRIP affects ACB: When a dividend is reinvested, two things happen simultaneously:

1. The dividend is included in your income for the year (you receive a T5 or T3 slip)
2. The reinvested amount is added to your ACB (because you “purchased” new shares with it)

If you never track these DRIP additions to your ACB, you end up paying capital gains tax on an amount that already attracted income tax when it was declared as a dividend. This is double taxation — and it is your responsibility to avoid it, not the CRA’s.

DRIP ACB example

Starting position: 500 shares, ACB $25,000 ($50/share)

You added no new money — but your ACB grew by $1,275 because of DRIP reinvestments. If you sell eventually and fail to add this to your ACB, you will pay capital gains tax on that $1,275 a second time.

Return of Capital (ROC): When Distributions Reduce ACB

Return of Capital (ROC) is a distribution that the CRA does not consider taxable income in the year received. Instead, it reduces your ACB — effectively deferring the tax until you sell.

ROC is common in:

• Canadian income-focused ETFs and mutual funds
• Real estate investment trusts (REITs)
• Infrastructure and utility funds
• Some covered-call ETFs

Your T3 slip (Box 42) will show the ROC amount received. This amount must be subtracted from your ACB.

ROC example

Starting position: 1,000 shares, total ACB $25,000 ($25/share)

You receive $1,200 in distributions for the year. Your T3 shows:

• Box 32 (eligible dividends): $700 — taxable now
• Box 42 (return of capital): $500 — reduces ACB

The $500 is not gone — when you eventually sell, your lower ACB creates a larger capital gain, and that is when you pay the deferred tax.

Warning: If ROC distributions are large enough to reduce your ACB below zero, the negative amount becomes an immediate capital gain even if you have not sold. This is rare but can happen with high-distribution funds held for many years.

ACB for ETFs and Mutual Funds: Reinvested Distributions

Funds can distribute income in several ways, and each has a different effect on ACB:

The T3 slip you receive from your fund or ETF provider breaks down each distribution type. Your broker’s year-end tax documents should also include this detail. However, your broker’s ACB tracking is often incomplete — particularly for DRIP and ROC — so you should maintain your own records.

Foreign Securities: Track ACB in Canadian Dollars

When you hold US or other foreign stocks or ETFs in a non-registered account, you must track ACB in Canadian dollars, converting each transaction at the exchange rate on the date of the transaction.

USD stock example

ACB per share = $5,533 ÷ 100 = $55.33 CAD

When you sell: convert proceeds at the exchange rate on the sale date to CAD, then subtract the CAD ACB. Any foreign exchange gain or loss is embedded in your capital gain — it is not tracked separately.

The Bank of Canada’s daily exchange rates are the accepted source for conversions: bankofcanada.ca/rates/exchange.

The Superficial Loss Rule

The superficial loss rule prevents investors from harvesting a capital loss while maintaining the same investment position. If you sell a security at a loss and repurchase the same or identical security within 30 days before or after the sale — or if an affiliated person does so — the loss is denied.

The denied loss is not eliminated permanently. It is added to the ACB of the replacement shares, deferring the loss until you truly exit the position.

Superficial loss example

You own 200 shares of an ETF with ACB of $10,000. The market drops and you sell for $7,500 — a $2,500 loss.

Scenario A — You wait 31+ days to repurchase:

• Capital loss of $2,500 is fully claimable against capital gains

Scenario B — You repurchase 15 days later at $7,600:

• Loss of $2,500 is denied (superficial loss)
• Your new ACB = $7,600 (repurchase price) + $2,500 (denied loss) = $10,100
• The economic loss is preserved in your ACB and will be realized when you eventually sell

Affiliated persons for this rule include your spouse or common-law partner, a corporation controlled by you or your spouse, and certain trusts. A common loss-harvesting strategy is to sell one ETF and immediately buy a similar — but not identical — ETF tracking a different index. For example, selling XIU (iShares S&P/TSX 60) and purchasing XIC (iShares S&P/TSX Composite) is generally considered acceptable, though the “identical property” analysis is fact-specific.

Tools to Track ACB

Tracking ACB manually in a spreadsheet works, but it becomes complex for a large portfolio with frequent DRIP and multiple accounts. The key is to record every transaction consistently.

For each transaction, record:

• Date
• Security name and ticker
• Transaction type (buy, sell, DRIP, ROC adjustment, corporate action)
• Shares bought, sold, or added
• Price per share in CAD (convert if foreign)
• Commission
• Running total shares, total ACB, and ACB per share after the transaction

Free and paid tools:

• AdjustedCostBase.ca — purpose-built free Canadian ACB tracker with DRIP and ROC support
• Spreadsheet (Google Sheets or Excel) — fully custom, no third-party dependency; works well for straightforward portfolios
• Wealthica / Sharesight — portfolio aggregators that can track ACB, though DRIP and ROC accuracy varies by platform

Your T5008 slip from your broker lists proceeds and cost for each disposition, which helps reconcile sales — but the cost reported on a T5008 often does not reflect the correct ACB (especially where DRIP or ROC is involved), so never use it as your sole source. See our T5008 slip guide for more detail on how to read that slip correctly.

Common ACB Mistakes

Key Takeaways

• ACB is the weighted average cost of your investment, including all purchases and commissions
• Canada requires the weighted average method — you cannot choose which specific shares to sell (no FIFO)
• DRIP reinvestments increase ACB; Return of Capital decreases it — both must be tracked meticulously in non-registered accounts
• Foreign securities must have ACB tracked in Canadian dollars using the Bank of Canada rate at each transaction date
• The superficial loss rule denies losses when you repurchase within 30 days, but defers rather than eliminates the loss through an ACB adjustment
• ACB only applies to non-registered accounts — no tracking required inside a TFSA, RRSP, FHSA, or RESP

Related: Capital Gains Tax in Canada · Capital Gains Inclusion Rate · T5008 Slip Explained · Investment Tax Hub